diff --git a/Arrangement_2/include/CGAL/IO/Arrangement_2_writer.h b/Arrangement_2/include/CGAL/IO/Arrangement_2_writer.h
index 94e49c87e7c..3a18ce6f2fa 100644
--- a/Arrangement_2/include/CGAL/IO/Arrangement_2_writer.h
+++ b/Arrangement_2/include/CGAL/IO/Arrangement_2_writer.h
@@ -325,7 +325,7 @@ protected:
   /*! Get the number of edges along a given CCB. */
   std::size_t _circulator_size (Ccb_halfedge_const_circulator circ) const
   {
-    CGAL_assertion (circ != CGAL_NULL);
+    CGAL_assertion (circ != NULL);
 
     std::size_t                    n = 0;
     Ccb_halfedge_const_circulator  curr = circ;
diff --git a/Circulator/include/CGAL/Safe_circulator_from_iterator.h b/Circulator/include/CGAL/Safe_circulator_from_iterator.h
index 3a88df7b955..fabdcfd2472 100644
--- a/Circulator/include/CGAL/Safe_circulator_from_iterator.h
+++ b/Circulator/include/CGAL/Safe_circulator_from_iterator.h
@@ -93,11 +93,11 @@ public:
 //
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return m_empty;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     
     bool operator==( const Self& c) const
     {
diff --git a/Circulator/include/CGAL/circulator.h b/Circulator/include/CGAL/circulator.h
index 02f568be948..744733068c1 100644
--- a/Circulator/include/CGAL/circulator.h
+++ b/Circulator/include/CGAL/circulator.h
@@ -307,7 +307,7 @@ void Assert_is_at_least_random_access_category( const IC& /*ic*/) {
 
 template< class C> inline
 bool I_is_empty_range( const C& c1, const C&, Circulator_tag){
-    return c1 == CGAL_NULL;
+    return c1 == NULL;
 }
 
 template< class I> inline
@@ -364,7 +364,7 @@ I_min_circulator_size( const C& c) {
     Assert_random_access_category(c);
     typedef typename C::size_type  size_type;
     size_type n = 0;
-    if ( c != CGAL_NULL) {
+    if ( c != NULL) {
         n = (c-1) - c + 1;
         CGAL_assertion(n > 0);
     }
@@ -375,7 +375,7 @@ template <class C>
 typename C::size_type
 I_circulator_size( const C& c, Forward_circulator_tag) {
     // Simply count.
-    if ( c == CGAL_NULL)
+    if ( c == NULL)
         return 0;
     typedef typename C::size_type  size_type;
     size_type n = 0;
@@ -408,7 +408,7 @@ template <class C>
 typename C::difference_type
 I_circulator_distance( C c, const C& d, Forward_circulator_tag) {
     // Simply count.
-    if ( c == CGAL_NULL)
+    if ( c == NULL)
         return 0;
     typedef typename C::difference_type  difference_type;
     difference_type n = 0;
@@ -547,18 +547,18 @@ public:
         return !(*this == i);
     }
     Ref  operator*() const {
-        CGAL_assertion( m_anchor != CGAL_NULL);
-        CGAL_assertion( current  != CGAL_NULL);
+        CGAL_assertion( m_anchor != NULL);
+        CGAL_assertion( current  != NULL);
         return Ref(*current);
     }
     Ptr  operator->() const {
-        CGAL_assertion( m_anchor != CGAL_NULL);
-        CGAL_assertion( current  != CGAL_NULL);
+        CGAL_assertion( m_anchor != NULL);
+        CGAL_assertion( current  != NULL);
         return Ptr(current.operator->());
     }
     Self& operator++() {
-        CGAL_assertion( m_anchor != CGAL_NULL);
-        CGAL_assertion( current  != CGAL_NULL);
+        CGAL_assertion( m_anchor != NULL);
+        CGAL_assertion( current  != NULL);
         ++current;
         if ( current == *m_anchor)
             ++m_winding;
@@ -570,8 +570,8 @@ public:
         return tmp;
     }
     Self& operator--() {
-        CGAL_assertion( m_anchor != CGAL_NULL);
-        CGAL_assertion( current != CGAL_NULL);
+        CGAL_assertion( m_anchor != NULL);
+        CGAL_assertion( current != NULL);
         if ( current == *m_anchor)
             --m_winding;
         --current;
@@ -583,8 +583,8 @@ public:
         return tmp;
     }
     Self& operator+=( difference_type n) {
-        CGAL_assertion( m_anchor != CGAL_NULL);
-        CGAL_assertion( current != CGAL_NULL);
+        CGAL_assertion( m_anchor != NULL);
+        CGAL_assertion( current != NULL);
         if ( n < 0 && current == *m_anchor)  // We are leaving the anchor.
             --m_winding;
         current += n;
@@ -604,8 +604,8 @@ public:
         return tmp += -n;
     }
     difference_type  operator-( const Self& i) const {
-        CGAL_assertion( m_anchor  != CGAL_NULL);
-        CGAL_assertion( current   != CGAL_NULL);
+        CGAL_assertion( m_anchor  != NULL);
+        CGAL_assertion( current   != NULL);
         CGAL_assertion( m_anchor  == i.m_anchor);
         if ( m_winding != i.m_winding) {
             difference_type s = I_min_circulator_size( *m_anchor);
@@ -621,8 +621,8 @@ public:
         return tmp.operator*();
     }
     bool operator<( const Self& i) const {
-        CGAL_assertion( m_anchor  != CGAL_NULL);
-        CGAL_assertion( current != CGAL_NULL);
+        CGAL_assertion( m_anchor  != NULL);
+        CGAL_assertion( current != NULL);
         CGAL_assertion( m_anchor  == i.m_anchor);
         return (     (m_winding < i.m_winding)
                  || (    (m_winding == i.m_winding)
@@ -693,12 +693,12 @@ typedef Iterator_from_circulator< C, const_reference, const_pointer>
     }
     iterator end() {
         // the past-the-end iterator.
-        return anchor == CGAL_NULL ?  iterator( &anchor, 0)
+        return anchor == NULL ?  iterator( &anchor, 0)
                                         :  iterator( &anchor, 1);
     }
     const_iterator end() const {
         // the past-the-end const iterator.
-        return anchor == CGAL_NULL ?  const_iterator( &anchor, 0)
+        return anchor == NULL ?  const_iterator( &anchor, 0)
                                         :  const_iterator( &anchor, 1);
     }
 };
@@ -741,11 +741,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return (ctnr == NULL) || (ctnr->begin() == ctnr->end());
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c) const { return i == c.i; }
     bool operator!=( const Self& c) const { return !(*this == c); }
     reference  operator*() const {
@@ -874,11 +874,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return (ctnr == NULL) || (ctnr->begin() == ctnr->end());
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c) const { return i == c.i; }
     bool operator!=( const Self& c) const { return !(*this == c); }
     reference  operator*() const {
@@ -1026,11 +1026,11 @@ public:
 //
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return empty;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c) const { return  current == c.current;}
     bool operator!=( const Self& c) const { return !(*this == c); }
     reference  operator*() const {
diff --git a/Circulator/include/CGAL/circulator_impl.h b/Circulator/include/CGAL/circulator_impl.h
index 103dcfdde54..e5fbeeb6b9d 100644
--- a/Circulator/include/CGAL/circulator_impl.h
+++ b/Circulator/include/CGAL/circulator_impl.h
@@ -65,11 +65,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     reference  operator*()             const { return *(S*)this->_ptr;}
@@ -108,11 +108,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     reference  operator*()             const { return *(const S*)this->_ptr;}
@@ -155,11 +155,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     reference  operator*()             const { return *(S*)this->_ptr;}
@@ -207,11 +207,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     reference  operator*()             const { return *(const S*)this->_ptr;}
@@ -266,11 +266,11 @@ public:
 //
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     C&   operator*()                   const { return *(C*)this->_ptr;}
@@ -304,11 +304,11 @@ public:
 // OPERATIONS
 
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     const C&  operator*()              const { return *(C*)this->_ptr;}
@@ -341,11 +341,11 @@ public:
 //
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     C&   operator*()                   const { return *(C*)this->_ptr;}
@@ -390,11 +390,11 @@ public:
 //
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return this->_ptr == NULL;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c)    const { return this->_ptr == c._ptr; }
     bool operator!=( const Self& c)    const { return !(*this == c); }
     const C&  operator*()              const { return *(C*)this->_ptr;}
@@ -462,11 +462,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return _i >= _size;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c) const {
         CGAL_assertion( this->_ptr  == c._ptr);  // belong to the same array?
         CGAL_assertion( _size == c._size); // same size when instantiated ?
@@ -586,11 +586,11 @@ public:
 //
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return _i >= _size;
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c) const {
         CGAL_assertion( this->_ptr  == c._ptr);  // belong to the same array?
         CGAL_assertion( _size == c._size); // same size when instantiated ?
diff --git a/Circulator/test/Circulator/test_circ1.cpp b/Circulator/test/Circulator/test_circ1.cpp
index 90b415766eb..691723a2da2 100644
--- a/Circulator/test/Circulator/test_circ1.cpp
+++ b/Circulator/test/Circulator/test_circ1.cpp
@@ -2375,11 +2375,11 @@ void test_circulator_from_iterator() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -2488,11 +2488,11 @@ void test_circulator_from_iterator() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -2730,11 +2730,11 @@ void test_circulator_from_iterator() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -2892,11 +2892,11 @@ void test_circulator_from_iterator() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -3303,11 +3303,11 @@ void test_circulator_from_iterator() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -3528,11 +3528,11 @@ void test_circulator_from_iterator() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -3737,11 +3737,11 @@ void test_circulator_from_container() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -3850,11 +3850,11 @@ void test_circulator_from_container() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -4092,11 +4092,11 @@ void test_circulator_from_container() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -4255,11 +4255,11 @@ void test_circulator_from_container() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -4666,11 +4666,11 @@ void test_circulator_from_container() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
@@ -4892,11 +4892,11 @@ void test_circulator_from_container() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = c;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == c);
         assert( i == c);
         // Do I reach myself.
diff --git a/Circulator/test/Circulator/test_circ2.cpp b/Circulator/test/Circulator/test_circ2.cpp
index 1cc3b2414fc..9a8b7919dc9 100644
--- a/Circulator/test/Circulator/test_circ2.cpp
+++ b/Circulator/test/Circulator/test_circ2.cpp
@@ -299,11 +299,11 @@ void test_struct(){
     
         // Check tests for empty data structures.
         Struct_circulator z = Struct_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Struct_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -408,11 +408,11 @@ void test_struct(){
     
         // Check tests for empty data structures.
         Struct_const_circulator z = Struct_const_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Struct_const_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -646,11 +646,11 @@ void test_struct(){
     
         // Check tests for empty data structures.
         Struct_bi_circulator z = Struct_bi_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Struct_bi_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -804,11 +804,11 @@ void test_struct(){
     
         // Check tests for empty data structures.
         Struct_bi_const_circulator z = Struct_bi_const_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Struct_bi_const_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -964,11 +964,11 @@ void test_class(){
     
         // Check tests for empty data structures.
         Class_circulator z = Class_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Class_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -1073,11 +1073,11 @@ void test_class(){
     
         // Check tests for empty data structures.
         Class_const_circulator z = Class_const_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Class_const_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -1311,11 +1311,11 @@ void test_class(){
     
         // Check tests for empty data structures.
         Class_bi_circulator z = Class_bi_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Class_bi_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -1469,11 +1469,11 @@ void test_class(){
     
         // Check tests for empty data structures.
         Class_bi_const_circulator z = Class_bi_const_circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Class_bi_const_circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -1886,11 +1886,11 @@ void test_array() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
@@ -2114,11 +2114,11 @@ void test_array() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        assert(   z == CGAL_NULL);
-        assert( ! (z != CGAL_NULL));
+        assert(   z == NULL);
+        assert( ! (z != NULL));
         Circulator i = start;
-        assert( ! (i == CGAL_NULL));
-        assert(   i != CGAL_NULL);
+        assert( ! (i == NULL));
+        assert(   i != NULL);
         assert( i == start);
         assert( i == start);
         // Do I reach myself.
diff --git a/HalfedgeDS/include/CGAL/HalfedgeDS_iterator.h b/HalfedgeDS/include/CGAL/HalfedgeDS_iterator.h
index fd40fb1b5b0..536993a9dca 100644
--- a/HalfedgeDS/include/CGAL/HalfedgeDS_iterator.h
+++ b/HalfedgeDS/include/CGAL/HalfedgeDS_iterator.h
@@ -56,11 +56,11 @@ public:
 
     // pointer  ptr() const { return & It::operator*();}
 
-    bool operator==( CGAL_NULL_TYPE CGAL_assertion_code(p)) const {
+    bool operator==( Nullptr_t CGAL_assertion_code(p)) const {
         CGAL_assertion( p == 0);
         return It::operator==( It());
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& i)    const { return  It::operator==(i); }
     bool operator!=( const Self& i)    const { return !(*this == i); }
 
@@ -116,11 +116,11 @@ public:
 
     // pointer  ptr() const { return & It::operator*();}
 
-    bool operator==( CGAL_NULL_TYPE CGAL_assertion_code(p)) const {
+    bool operator==( Nullptr_t CGAL_assertion_code(p)) const {
         CGAL_assertion( p == 0);
         return It::operator==( It());
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& i)    const { return  It::operator==(i); }
     bool operator!=( const Self& i)    const { return !(*this == i); }
 
@@ -194,11 +194,11 @@ public:
 
     pointer  ptr() const { return & It::operator*();}
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return It::operator==( It(NULL));
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& i) const { return  It::operator==(i); }
     bool operator!=( const Self& i) const { return !(*this == i); }
 
@@ -257,11 +257,11 @@ public:
 
     pointer  ptr() const { return & It::operator*();}
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return It::operator==( It(NULL));
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& i) const { return  It::operator==(i); }
     bool operator!=( const Self& i) const { return !(*this == i); }
 
@@ -315,11 +315,11 @@ public:
 
     pointer  ptr() const { return & It::operator*();}
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return It::operator==( It(NULL));
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& i) const { return  It::operator==(i); }
     bool operator!=( const Self& i) const { return !(*this == i); }
 
@@ -378,11 +378,11 @@ public:
 
     pointer  ptr() const { return & It::operator*();}
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return It::operator==( It(NULL));
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& i) const { return  It::operator==(i); }
     bool operator!=( const Self& i) const { return !(*this == i); }
 
diff --git a/Installation/include/CGAL/config.h b/Installation/include/CGAL/config.h
index eee44e036c8..a1fa8a88a7f 100644
--- a/Installation/include/CGAL/config.h
+++ b/Installation/include/CGAL/config.h
@@ -27,7 +27,6 @@
 #define CGAL_CONFIG_H
 
 
-
 #ifdef CGAL_INCLUDE_WINDOWS_DOT_H
 // Mimic users including this file which defines min max macros
 // and other names leading to name clashes
@@ -211,23 +210,11 @@ using std::max;
 #endif
 
 
-// Macros for NULL and the NULL type.
-#include <cstddef>
+CGAL_BEGIN_NAMESPACE
 
-#ifndef CGAL_NULL_TYPE
-// Why is this GCC specific?  Let's try to remove this.
-#if 0
-#  if defined( __GNUG__ )
-#    define CGAL_NULL_TYPE const void*
-#    define CGAL_NULL 0
-#  else // __GNUG__ //
-#    define CGAL_NULL_TYPE int
-#    define CGAL_NULL NULL
-#  endif // __GNUG__ //
-#else
-#  define CGAL_NULL_TYPE const void *
-#  define CGAL_NULL NULL
-#endif
-#endif // CGAL_NULL_TYPE
+// Typedef for the type of NULL.
+typedef const void * Nullptr_t;   // Anticipate C++0x's std::nullptr_t
+
+CGAL_END_NAMESPACE
 
 #endif // CGAL_CONFIG_H
diff --git a/Mesh_2/include/CGAL/Filter_circulator.h b/Mesh_2/include/CGAL/Filter_circulator.h
index 4a4759383b4..f9f0af24c78 100644
--- a/Mesh_2/include/CGAL/Filter_circulator.h
+++ b/Mesh_2/include/CGAL/Filter_circulator.h
@@ -63,11 +63,11 @@ public:
 	}
     };
 
-  bool operator==( CGAL_NULL_TYPE ) const {
+  bool operator==( Nullptr_t ) const {
     return is_null;
   }
 
-  bool operator!=( CGAL_NULL_TYPE ) const {
+  bool operator!=( Nullptr_t ) const {
     return !is_null;
   }
 
diff --git a/Nef_2/include/CGAL/Nef_2/Object_handle.h b/Nef_2/include/CGAL/Nef_2/Object_handle.h
index 01f4c650ecf..957866d25ac 100644
--- a/Nef_2/include/CGAL/Nef_2/Object_handle.h
+++ b/Nef_2/include/CGAL/Nef_2/Object_handle.h
@@ -71,9 +71,9 @@ public:
 
   bool is_empty() const
   { empty E; return assign(E); }
-  bool operator==(CGAL_NULL_TYPE n) const
+  bool operator==(Nullptr_t n) const
   { CGAL_assertion(n == 0); return is_empty(); }
-  bool operator!=(CGAL_NULL_TYPE n) const
+  bool operator!=(Nullptr_t n) const
   { CGAL_assertion(n == 0); return !is_empty(); }
 
 };
diff --git a/Nef_2/include/CGAL/Nef_2/iterator_tools.h b/Nef_2/include/CGAL/Nef_2/iterator_tools.h
index d33bf27ec39..75c1e139486 100644
--- a/Nef_2/include/CGAL/Nef_2/iterator_tools.h
+++ b/Nef_2/include/CGAL/Nef_2/iterator_tools.h
@@ -39,11 +39,11 @@ public:
 // OPERATIONS Forward Category
 // ---------------------------
 
-    bool operator==( CGAL_NULL_TYPE p ) const {
+    bool operator==( Nullptr_t p ) const {
       CGAL_assertion( p == NULL );
       return Iter::operator==( Iter(NULL) );
     }
-    bool operator!=( CGAL_NULL_TYPE p ) const {
+    bool operator!=( Nullptr_t p ) const {
       return !(*this == p);
     }
     bool operator==( const Self& i ) const {
diff --git a/Polygon/include/CGAL/Polygon_2/Polygon_2_edge_circulator.h b/Polygon/include/CGAL/Polygon_2/Polygon_2_edge_circulator.h
index 7030125b96e..3b9e70873cb 100644
--- a/Polygon/include/CGAL/Polygon_2/Polygon_2_edge_circulator.h
+++ b/Polygon/include/CGAL/Polygon_2/Polygon_2_edge_circulator.h
@@ -68,12 +68,12 @@ class Polygon_2_const_edge_circulator {
     Polygon_2_const_edge_circulator(Vertex_const_circulator f)
       : first_vertex(f) {}
 
-    bool operator==( CGAL_NULL_TYPE p ) const {
+    bool operator==( Nullptr_t p ) const {
       CGAL_polygon_assertion( p == 0);
       return (first_vertex == 0);
     }
 
-    bool operator!=( CGAL_NULL_TYPE p ) const
+    bool operator!=( Nullptr_t p ) const
     {
       return !(*this == p);
     }
diff --git a/Polygon/include/CGAL/Polygon_2/Polygon_2_vertex_circulator.h b/Polygon/include/CGAL/Polygon_2/Polygon_2_vertex_circulator.h
index 42fa2263677..ea07f536fe4 100644
--- a/Polygon/include/CGAL/Polygon_2/Polygon_2_vertex_circulator.h
+++ b/Polygon/include/CGAL/Polygon_2/Polygon_2_vertex_circulator.h
@@ -71,11 +71,11 @@ public:
 
 // OPERATIONS
 
-    bool operator==( CGAL_NULL_TYPE p) const {
-        CGAL_assertion( p == CGAL_NULL);
+    bool operator==( Nullptr_t p) const {
+        CGAL_assertion( p == NULL);
         return (ctnr == NULL) || (ctnr->begin() == ctnr->end());
     }
-    bool operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+    bool operator!=( Nullptr_t p) const { return !(*this == p); }
     bool operator==( const Self& c) const { return i == c.i; }
     bool operator!=( const Self& c) const { return !(*this == c); }
     reference  operator*() const {
diff --git a/Qt_widget/include/CGAL/apply_to_range.h b/Qt_widget/include/CGAL/apply_to_range.h
index f887a3e0ca3..49ed706f777 100644
--- a/Qt_widget/include/CGAL/apply_to_range.h
+++ b/Qt_widget/include/CGAL/apply_to_range.h
@@ -67,8 +67,8 @@ void apply_to_range(const Tr &t,
   l4 = t.line_walk(POINT(xr_left, yr_bottom), POINT(xr_left, yr_top), hface4);
 
   //test if everything is inside or outside
-  if( (l1 == (CGAL_NULL_TYPE) NULL) && (l2 == (CGAL_NULL_TYPE) NULL) &&
-      (l3 == (CGAL_NULL_TYPE) NULL) && (l4 == (CGAL_NULL_TYPE) NULL)) 
+  if( (l1 == (Nullptr_t) NULL) && (l2 == (Nullptr_t) NULL) &&
+      (l3 == (Nullptr_t) NULL) && (l4 == (Nullptr_t) NULL)) 
   {
     FVI v = t.finite_vertices_begin();
     if((*v).point().x() < xr_left || (*v).point().x() > xr_right || 
@@ -88,7 +88,7 @@ void apply_to_range(const Tr &t,
   //if we are here, then a part of the triangulation is inside, the other is outside
 
   //put all the faces on the boundaries in the stack and the map
-  if(l1 != (CGAL_NULL_TYPE) NULL) //found at least one face that intersect the TOP segment
+  if(l1 != (Nullptr_t) NULL) //found at least one face that intersect the TOP segment
   {
     while (t.is_infinite(l1)) l1++; //we should start with a finite face
     do{                             //put all of them in the stack;
@@ -98,7 +98,7 @@ void apply_to_range(const Tr &t,
     }while(!t.is_infinite(l1) && 
 	   t.triangle(l1).has_on_unbounded_side(POINT(xr_right, yr_top)));
   }
-  if(l2 != (CGAL_NULL_TYPE) NULL) //found at least one face that intersect the RIGHT segment
+  if(l2 != (Nullptr_t) NULL) //found at least one face that intersect the RIGHT segment
   {
     while (t.is_infinite(l2)) l2++; //we should start with a finite face
     do{                             //put all of them in the stack;
@@ -110,7 +110,7 @@ void apply_to_range(const Tr &t,
     }while(!t.is_infinite(l2) && 
 	   t.triangle(l2).has_on_unbounded_side(POINT(xr_right, yr_bottom)));
   }
-  if(l3 != (CGAL_NULL_TYPE) NULL) //found at least one face that intersect the BOTTOM segment
+  if(l3 != (Nullptr_t) NULL) //found at least one face that intersect the BOTTOM segment
   {
     while (t.is_infinite(l3)) l3++; //we should start with a finite face
     do{                             //put all of them in the stack;
@@ -122,7 +122,7 @@ void apply_to_range(const Tr &t,
     }while(!t.is_infinite(l3) && 
 	   t.triangle(l3).has_on_unbounded_side(POINT(xr_left, yr_bottom)));
   }
-  if(l4 != (CGAL_NULL_TYPE) NULL) //found at least one face that intersect the LEFT segment
+  if(l4 != (Nullptr_t) NULL) //found at least one face that intersect the LEFT segment
   {
     while (t.is_infinite(l4)) l4++; //we should start with a finite face
     do{                             //put all of them in the stack;
diff --git a/STL_Extension/include/CGAL/Circulator_identity.h b/STL_Extension/include/CGAL/Circulator_identity.h
index a23e32b6715..062fb8b6606 100644
--- a/STL_Extension/include/CGAL/Circulator_identity.h
+++ b/STL_Extension/include/CGAL/Circulator_identity.h
@@ -57,11 +57,11 @@ public:
 
   Circulator  current_circulator() const { return nt;}
 
-  bool operator==( CGAL_NULL_TYPE p) const {
+  bool operator==( Nullptr_t p) const {
     CGAL_assertion( p == 0);
     return ( nt == 0);                                    //###//
   }
-  bool operator!=( CGAL_NULL_TYPE p) const {
+  bool operator!=( Nullptr_t p) const {
     return !(*this == p);
   }
   bool operator==( const Self& i) const {
diff --git a/STL_Extension/include/CGAL/Circulator_on_node.h b/STL_Extension/include/CGAL/Circulator_on_node.h
index d661ebf89af..65442037200 100644
--- a/STL_Extension/include/CGAL/Circulator_on_node.h
+++ b/STL_Extension/include/CGAL/Circulator_on_node.h
@@ -59,11 +59,11 @@ public:
 
   Ptr  ptr() const { return nt;}
 
-  bool operator==( CGAL_NULL_TYPE p) const {
+  bool operator==( Nullptr_t p) const {
     CGAL_assertion( p == 0);
     return ( nt == 0);
   }
-  bool  operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+  bool  operator!=( Nullptr_t p) const { return !(*this == p); }
   bool  operator==( const Self& i) const { return ( nt == i.nt); }
   bool  operator!=( const Self& i) const { return !(*this == i); }
   Ref   operator*()  const { return *nt; }
diff --git a/STL_Extension/include/CGAL/Circulator_project.h b/STL_Extension/include/CGAL/Circulator_project.h
index 3f818e2cc61..f504e731c1b 100644
--- a/STL_Extension/include/CGAL/Circulator_project.h
+++ b/STL_Extension/include/CGAL/Circulator_project.h
@@ -62,11 +62,11 @@ public:
     return &(fct(*nt));
   }
 
-  bool operator==( CGAL_NULL_TYPE p) const {
+  bool operator==( Nullptr_t p) const {
     CGAL_assertion( p == 0);
     return ( nt == 0);
   }
-  bool  operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+  bool  operator!=( Nullptr_t p) const { return !(*this == p); }
   bool  operator==( const Self& i) const { return ( nt == i.nt); }
   bool  operator!=( const Self& i) const { return !(*this == i); }
   Ref   operator*()  const { return *ptr(); }
diff --git a/STL_Extension/include/CGAL/Compact_container.h b/STL_Extension/include/CGAL/Compact_container.h
index 18daccf24c8..01ccfb0cc24 100644
--- a/STL_Extension/include/CGAL/Compact_container.h
+++ b/STL_Extension/include/CGAL/Compact_container.h
@@ -686,7 +686,7 @@ namespace CGALi {
     }
 
     // Construction from NULL
-    CC_iterator (CGAL_NULL_TYPE CGAL_assertion_code(n))
+    CC_iterator (Nullptr_t CGAL_assertion_code(n))
     {
       CGAL_assertion (n == NULL);
       m_ptr.p = NULL;
@@ -804,7 +804,7 @@ namespace CGALi {
   template < class DSC, bool Const >
   inline
   bool operator==(const CC_iterator<DSC, Const> &rhs,
-                  CGAL_NULL_TYPE CGAL_assertion_code(n))
+                  Nullptr_t CGAL_assertion_code(n))
   {
     CGAL_assertion( n == NULL);
     return &*rhs == NULL;
@@ -813,7 +813,7 @@ namespace CGALi {
   template < class DSC, bool Const >
   inline
   bool operator!=(const CC_iterator<DSC, Const> &rhs,
-		  CGAL_NULL_TYPE CGAL_assertion_code(n))
+		  Nullptr_t CGAL_assertion_code(n))
   {
     CGAL_assertion( n == NULL);
     return &*rhs != NULL;
diff --git a/STL_Extension/include/CGAL/iterator.h b/STL_Extension/include/CGAL/iterator.h
index 6fc83b8fa09..7d60c216fc0 100644
--- a/STL_Extension/include/CGAL/iterator.h
+++ b/STL_Extension/include/CGAL/iterator.h
@@ -309,11 +309,11 @@ public:
   Circulator  current_circulator() const { return nt;}
 
   Iterator  current_iterator() const { return nt;}
-  bool operator==( CGAL_NULL_TYPE p) const {
+  bool operator==( Nullptr_t p) const {
     CGAL_assertion( p == 0);
     return empty;
   }
-  bool  operator!=( CGAL_NULL_TYPE p) const { return !(*this == p); }
+  bool  operator!=( Nullptr_t p) const { return !(*this == p); }
   bool  operator==( const Self& i) const { return (empty && i.empty) ||( nt == i.nt); }
   bool  operator!=( const Self& i) const { return !(*this == i); }
   reference operator*()  const { return *nt; }
diff --git a/STL_Extension/test/STL_Extension/test_stl_extension.cpp b/STL_Extension/test/STL_Extension/test_stl_extension.cpp
index c0cf8667660..823853d88aa 100644
--- a/STL_Extension/test/STL_Extension/test_stl_extension.cpp
+++ b/STL_Extension/test/STL_Extension/test_stl_extension.cpp
@@ -1357,11 +1357,11 @@ void test_Circulator_identity() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -1522,11 +1522,11 @@ Assert_bidirectional_category(c_begin);
 
     // Check tests for empty data structures.
     C_Circulator z = C_Circulator();
-    CGAL_assertion(   z == CGAL_NULL);
-    CGAL_assertion( ! (z != CGAL_NULL));
+    CGAL_assertion(   z == NULL);
+    CGAL_assertion( ! (z != NULL));
     C_Circulator i = c_begin;
-    CGAL_assertion( ! (i == CGAL_NULL));
-    CGAL_assertion(   i != CGAL_NULL);
+    CGAL_assertion( ! (i == NULL));
+    CGAL_assertion(   i != NULL);
     CGAL_assertion( i == c_begin);
     CGAL_assertion( i == c_begin);
     // Do I reach myself.
@@ -1944,11 +1944,11 @@ l2.destroy();
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -2175,11 +2175,11 @@ Assert_random_access_category(c_begin);
 
     // Check tests for empty data structures.
     C_Circulator z = C_Circulator();
-    CGAL_assertion(   z == CGAL_NULL);
-    CGAL_assertion( ! (z != CGAL_NULL));
+    CGAL_assertion(   z == NULL);
+    CGAL_assertion( ! (z != NULL));
     C_Circulator i = c_begin;
-    CGAL_assertion( ! (i == CGAL_NULL));
-    CGAL_assertion(   i != CGAL_NULL);
+    CGAL_assertion( ! (i == NULL));
+    CGAL_assertion(   i != NULL);
     CGAL_assertion( i == c_begin);
     CGAL_assertion( i == c_begin);
     // Do I reach myself.
@@ -4469,11 +4469,11 @@ void test_Circulator_project() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -4634,11 +4634,11 @@ Assert_bidirectional_category(c_begin);
 
     // Check tests for empty data structures.
     C_Circulator z = C_Circulator();
-    CGAL_assertion(   z == CGAL_NULL);
-    CGAL_assertion( ! (z != CGAL_NULL));
+    CGAL_assertion(   z == NULL);
+    CGAL_assertion( ! (z != NULL));
     C_Circulator i = c_begin;
-    CGAL_assertion( ! (i == CGAL_NULL));
-    CGAL_assertion(   i != CGAL_NULL);
+    CGAL_assertion( ! (i == NULL));
+    CGAL_assertion(   i != NULL);
     CGAL_assertion( i == c_begin);
     CGAL_assertion( i == c_begin);
     // Do I reach myself.
@@ -4900,11 +4900,11 @@ l2.destroy();
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -5065,11 +5065,11 @@ Assert_bidirectional_category(c_begin);
 
     // Check tests for empty data structures.
     C_Circulator z = C_Circulator();
-    CGAL_assertion(   z == CGAL_NULL);
-    CGAL_assertion( ! (z != CGAL_NULL));
+    CGAL_assertion(   z == NULL);
+    CGAL_assertion( ! (z != NULL));
     C_Circulator i = c_begin;
-    CGAL_assertion( ! (i == CGAL_NULL));
-    CGAL_assertion(   i != CGAL_NULL);
+    CGAL_assertion( ! (i == NULL));
+    CGAL_assertion(   i != NULL);
     CGAL_assertion( i == c_begin);
     CGAL_assertion( i == c_begin);
     // Do I reach myself.
@@ -5489,11 +5489,11 @@ l2.destroy();
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -5720,11 +5720,11 @@ Assert_random_access_category(c_begin);
 
     // Check tests for empty data structures.
     C_Circulator z = C_Circulator();
-    CGAL_assertion(   z == CGAL_NULL);
-    CGAL_assertion( ! (z != CGAL_NULL));
+    CGAL_assertion(   z == NULL);
+    CGAL_assertion( ! (z != NULL));
     C_Circulator i = c_begin;
-    CGAL_assertion( ! (i == CGAL_NULL));
-    CGAL_assertion(   i != CGAL_NULL);
+    CGAL_assertion( ! (i == NULL));
+    CGAL_assertion(   i != NULL);
     CGAL_assertion( i == c_begin);
     CGAL_assertion( i == c_begin);
     // Do I reach myself.
@@ -5923,11 +5923,11 @@ void test_Circulator_on_node() {
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -6038,11 +6038,11 @@ void test_Circulator_on_node() {
     
         // Check tests for empty data structures.
         C_Circulator z = C_Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         C_Circulator i = c_begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == c_begin);
         CGAL_assertion( i == c_begin);
         // Do I reach myself.
@@ -7347,11 +7347,11 @@ l2.destroy();
     
         // Check tests for empty data structures.
         Circulator z = Circulator();
-        CGAL_assertion(   z == CGAL_NULL);
-        CGAL_assertion( ! (z != CGAL_NULL));
+        CGAL_assertion(   z == NULL);
+        CGAL_assertion( ! (z != NULL));
         Circulator i = begin;
-        CGAL_assertion( ! (i == CGAL_NULL));
-        CGAL_assertion(   i != CGAL_NULL);
+        CGAL_assertion( ! (i == NULL));
+        CGAL_assertion(   i != NULL);
         CGAL_assertion( i == begin);
         CGAL_assertion( i == begin);
         // Do I reach myself.
@@ -7577,11 +7577,11 @@ Assert_random_access_category(c_begin);
 
     // Check tests for empty data structures.
     C_Circulator z = C_Circulator();
-    CGAL_assertion(   z == CGAL_NULL);
-    CGAL_assertion( ! (z != CGAL_NULL));
+    CGAL_assertion(   z == NULL);
+    CGAL_assertion( ! (z != NULL));
     C_Circulator i = c_begin;
-    CGAL_assertion( ! (i == CGAL_NULL));
-    CGAL_assertion(   i != CGAL_NULL);
+    CGAL_assertion( ! (i == NULL));
+    CGAL_assertion(   i != NULL);
     CGAL_assertion( i == c_begin);
     CGAL_assertion( i == c_begin);
     // Do I reach myself.
@@ -8348,11 +8348,11 @@ void test_N_step_adaptor_derived() {
         
             // Check tests for empty data structures.
             Circulator z = Circulator();
-            CGAL_assertion(   z == CGAL_NULL);
-            CGAL_assertion( ! (z != CGAL_NULL));
+            CGAL_assertion(   z == NULL);
+            CGAL_assertion( ! (z != NULL));
             Circulator i = begin;
-            CGAL_assertion( ! (i == CGAL_NULL));
-            CGAL_assertion(   i != CGAL_NULL);
+            CGAL_assertion( ! (i == NULL));
+            CGAL_assertion(   i != NULL);
             CGAL_assertion( i == begin);
             CGAL_assertion( i == begin);
             // Do I reach myself.
@@ -8578,11 +8578,11 @@ void test_N_step_adaptor_derived() {
         
             // Check tests for empty data structures.
             C_Circulator z = C_Circulator();
-            CGAL_assertion(   z == CGAL_NULL);
-            CGAL_assertion( ! (z != CGAL_NULL));
+            CGAL_assertion(   z == NULL);
+            CGAL_assertion( ! (z != NULL));
             C_Circulator i = c_begin;
-            CGAL_assertion( ! (i == CGAL_NULL));
-            CGAL_assertion(   i != CGAL_NULL);
+            CGAL_assertion( ! (i == NULL));
+            CGAL_assertion(   i != NULL);
             CGAL_assertion( i == c_begin);
             CGAL_assertion( i == c_begin);
             // Do I reach myself.
diff --git a/Straight_skeleton_2/include/CGAL/Straight_skeleton_vertex_base_2.h b/Straight_skeleton_2/include/CGAL/Straight_skeleton_vertex_base_2.h
index 93a0bdeb872..07400f11101 100644
--- a/Straight_skeleton_2/include/CGAL/Straight_skeleton_vertex_base_2.h
+++ b/Straight_skeleton_2/include/CGAL/Straight_skeleton_vertex_base_2.h
@@ -76,14 +76,14 @@ protected :
         ( Halfedge_circulator_base<OtherHalfedgeHandle,OtherAccessPolicy> const& aOther )
         : mHandle(aOther.mHandle) {}
 
-      bool operator==( CGAL_NULL_TYPE p ) const 
+      bool operator==( Nullptr_t p ) const 
       {
-        CGAL_assertion( p == CGAL_NULL ); 
+        CGAL_assertion( p == NULL ); 
         HalfedgeHandle null ;
         return mHandle == null ;
       }
       
-      bool operator!=( CGAL_NULL_TYPE p ) const { return !(*this == p); }
+      bool operator!=( Nullptr_t p ) const { return !(*this == p); }
       
     private :
 
diff --git a/Surface_mesh_parameterization/include/CGAL/Convertible_circulator_project.h b/Surface_mesh_parameterization/include/CGAL/Convertible_circulator_project.h
index 37552db864b..d9a80185059 100644
--- a/Surface_mesh_parameterization/include/CGAL/Convertible_circulator_project.h
+++ b/Surface_mesh_parameterization/include/CGAL/Convertible_circulator_project.h
@@ -57,8 +57,8 @@ public:
   /// OPERATIONS Forward Category
   /// ---------------------------
 
-    bool  operator==(CGAL_NULL_TYPE ptr) const { return (const Base&)*this == ptr; }
-    bool  operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool  operator==(Nullptr_t ptr) const { return (const Base&)*this == ptr; }
+    bool  operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
     bool  operator==(const Self& cir)    const { return (const Base&)*this == cir; }
     bool  operator!=(const Self& cir)    const { return ! (*this == cir); }
 
diff --git a/Surface_mesh_parameterization/include/CGAL/Convertible_filter_iterator.h b/Surface_mesh_parameterization/include/CGAL/Convertible_filter_iterator.h
index 2d3cba62ab0..52945d4bec7 100644
--- a/Surface_mesh_parameterization/include/CGAL/Convertible_filter_iterator.h
+++ b/Surface_mesh_parameterization/include/CGAL/Convertible_filter_iterator.h
@@ -60,8 +60,8 @@ public:
   /// OPERATIONS Forward Category
   /// ---------------------------
 
-    bool  operator==(CGAL_NULL_TYPE ptr) const { return (const Base&)*this == ptr; }
-    bool  operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool  operator==(Nullptr_t ptr) const { return (const Base&)*this == ptr; }
+    bool  operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
     bool  operator==(const Self& it) const { return (const Base&)*this == it; }
     bool  operator!=(const Self& it) const { return ! (*this == it); }
 
diff --git a/Surface_mesh_parameterization/include/CGAL/Convertible_iterator_project.h b/Surface_mesh_parameterization/include/CGAL/Convertible_iterator_project.h
index 8de672af949..ab4455834f9 100644
--- a/Surface_mesh_parameterization/include/CGAL/Convertible_iterator_project.h
+++ b/Surface_mesh_parameterization/include/CGAL/Convertible_iterator_project.h
@@ -55,8 +55,8 @@ public:
   /// OPERATIONS Forward Category
   /// ---------------------------
 
-    bool  operator==(CGAL_NULL_TYPE ptr) const { return (const Base&)*this == ptr; }
-    bool  operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool  operator==(Nullptr_t ptr) const { return (const Base&)*this == ptr; }
+    bool  operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
     bool  operator==(const Self& it) const { return (const Base&)*this == it; }
     bool  operator!=(const Self& it) const { return ! (*this == it); }
 
diff --git a/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_circulators.h b/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_circulators.h
index c5a714ab3ac..36a8a669fc2 100644
--- a/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_circulators.h
+++ b/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_circulators.h
@@ -136,8 +136,8 @@ public:
 
     bool operator==(const Self& cir)    const { return (const Base&)*this == cir; }
     bool operator!=(const Self& cir)    const { return !(*this == cir); }
-    bool operator==(CGAL_NULL_TYPE ptr) const { return (const Base&)*this == ptr; }
-    bool operator!=(CGAL_NULL_TYPE ptr) const { return !(*this == ptr); }
+    bool operator==(Nullptr_t ptr) const { return (const Base&)*this == ptr; }
+    bool operator!=(Nullptr_t ptr) const { return !(*this == ptr); }
 
     ///  operator*() and operator->() are inherited
 
@@ -522,8 +522,8 @@ public:
 /// OPERATIONS Forward Category
 /// ---------------------------
 
-    bool operator==(CGAL_NULL_TYPE ptr) const { return (const Base&)*this == ptr; }
-    bool operator!=(CGAL_NULL_TYPE ptr) const { return !(*this == ptr); }
+    bool operator==(Nullptr_t ptr) const { return (const Base&)*this == ptr; }
+    bool operator!=(Nullptr_t ptr) const { return !(*this == ptr); }
     bool operator==(const Self& cir)    const { return (const Base&)*this == cir; }
     bool operator!=(const Self& cir)    const { return !(*this == cir); }
 
diff --git a/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_iterators.h b/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_iterators.h
index c3d50081bfe..64f5d1d40d8 100644
--- a/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_iterators.h
+++ b/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_iterators.h
@@ -87,11 +87,11 @@ public:
     bool operator!=(const Self& it) const { return ! (*this == it); }
 
     /// Comparison to NULL pointer
-    bool operator==(CGAL_NULL_TYPE ptr) const {
+    bool operator==(Nullptr_t ptr) const {
         CGAL_surface_mesh_parameterization_assertion(ptr == NULL);
         return (const Base&)*this == Base();
     }
-    bool operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
 
     /// Conversion to handle
     operator Param_mesh_patch_vertex_handle<Adaptor>() const {
@@ -146,11 +146,11 @@ public:
     bool operator!=(const Self& it) const { return ! (*this == it); }
 
     /// Comparison to NULL pointer
-    bool operator==(CGAL_NULL_TYPE ptr) const {
+    bool operator==(Nullptr_t ptr) const {
         CGAL_surface_mesh_parameterization_assertion(ptr == NULL);
         return (const Base&)*this == Base();
     }
-    bool operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
 
     /// Conversion to handle
     operator Param_mesh_patch_vertex_const_handle<Adaptor>() const {
diff --git a/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_vertex.h b/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_vertex.h
index 278fecaf08a..e91c461aa35 100644
--- a/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_vertex.h
+++ b/Surface_mesh_parameterization/include/CGAL/Param_mesh_patch_vertex.h
@@ -267,11 +267,11 @@ public:
     bool operator!=(const Self& hdl) const { return ! (*this == hdl); }
 
     /// Comparison to NULL pointer
-    bool operator==(CGAL_NULL_TYPE ptr) const {
+    bool operator==(Nullptr_t ptr) const {
         CGAL_surface_mesh_parameterization_assertion(ptr == NULL);
         return m_ptr == NULL;
     }
-    bool operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
 
     pointer operator->()  const { return  m_ptr; }
     reference operator*() const { return *m_ptr; }
@@ -413,11 +413,11 @@ public:
     bool operator!=(const Self& hdl) const { return ! (*this == hdl); }
 
     /// Comparison to NULL pointer
-    bool operator==(CGAL_NULL_TYPE ptr) const {
+    bool operator==(Nullptr_t ptr) const {
         CGAL_surface_mesh_parameterization_assertion(ptr == NULL);
         return m_ptr == NULL;
     }
-    bool operator!=(CGAL_NULL_TYPE ptr) const { return ! (*this == ptr); }
+    bool operator!=(Nullptr_t ptr) const { return ! (*this == ptr); }
 
     pointer operator->()  const { return  m_ptr; }
     reference operator*() const { return *m_ptr; }
diff --git a/Triangulation_2/demo/Triangulation_2/delaunay_triangulation_2.cpp b/Triangulation_2/demo/Triangulation_2/delaunay_triangulation_2.cpp
index dfe84546293..bded718938f 100644
--- a/Triangulation_2/demo/Triangulation_2/delaunay_triangulation_2.cpp
+++ b/Triangulation_2/demo/Triangulation_2/delaunay_triangulation_2.cpp
@@ -177,7 +177,7 @@ private slots:
       widget->lock();
       Line_face_circulator lfc =
          tr1.line_walk(l.point(1), l.point(2)), done(lfc);
-      if(lfc == (CGAL_NULL_TYPE) NULL){
+      if(lfc == NULL){
       } else {
         *widget << CGAL::BLUE;
         *widget << CGAL::FillColor(CGAL::YELLOW);
diff --git a/Triangulation_2/include/CGAL/Triangulation_ds_circulators_2.h b/Triangulation_2/include/CGAL/Triangulation_ds_circulators_2.h
index 2b2660fafed..1edaf55078d 100644
--- a/Triangulation_2/include/CGAL/Triangulation_ds_circulators_2.h
+++ b/Triangulation_2/include/CGAL/Triangulation_ds_circulators_2.h
@@ -79,8 +79,8 @@ public:
   bool operator!=(const Face_handle &fh) const { return pos != fh; }
 
   bool is_empty() const;
-  bool operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const;
-  bool operator!=(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const;
+  bool operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const;
+  bool operator!=(Nullptr_t CGAL_triangulation_assertion_code(n)) const;
 
   Face&
   operator*() const
@@ -160,8 +160,8 @@ public:
   { return pos->vertex(_ri) != vh; }
 
   bool is_empty() const;
-  bool operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const;
-  bool operator!=(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const;
+  bool operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const;
+  bool operator!=(Nullptr_t CGAL_triangulation_assertion_code(n)) const;
 
   Vertex&
   operator*() const
@@ -239,8 +239,8 @@ public:
   bool operator==(const Edge_circulator &vc) const;
   bool operator!=(const Edge_circulator &vc) const;
   bool is_empty() const;
-  bool operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const;
-  bool operator!=(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const;
+  bool operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const;
+  bool operator!=(Nullptr_t CGAL_triangulation_assertion_code(n)) const;
 
   Edge*  operator->() const { 
     edge.first=pos;
@@ -357,7 +357,7 @@ return (_v == Vertex_handle() ||  pos == Face_handle() );
 template < class Tds >
 inline bool
 Triangulation_ds_face_circulator_2<Tds> ::
-operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return (_v == Vertex_handle() ||  pos == Face_handle() );  
@@ -366,7 +366,7 @@ operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
 template < class Tds >
 inline bool
 Triangulation_ds_face_circulator_2<Tds> ::
-operator!=(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator!=(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return ! (*this == NULL);
@@ -479,7 +479,7 @@ is_empty() const
 template < class Tds >
 inline bool
 Triangulation_ds_vertex_circulator_2<Tds> ::
-operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return (_v == Vertex_handle() || pos == Face_handle());
@@ -488,7 +488,7 @@ operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
 template < class Tds >
 inline bool
 Triangulation_ds_vertex_circulator_2<Tds> ::        
-operator!=(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator!=(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return !(*this == NULL);
@@ -599,7 +599,7 @@ is_empty() const
 template < class Tds >
 inline bool
 Triangulation_ds_edge_circulator_2<Tds> ::
-operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return (_v == Vertex_handle() || pos == Face_handle());
@@ -608,7 +608,7 @@ operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
 template < class Tds >
 inline bool
 Triangulation_ds_edge_circulator_2<Tds> ::
-operator!=(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator!=(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return !(*this == NULL);
diff --git a/Triangulation_2/include/CGAL/Triangulation_line_face_circulator_2.h b/Triangulation_2/include/CGAL/Triangulation_line_face_circulator_2.h
index 20972f77df5..d6a05791fed 100644
--- a/Triangulation_2/include/CGAL/Triangulation_line_face_circulator_2.h
+++ b/Triangulation_2/include/CGAL/Triangulation_line_face_circulator_2.h
@@ -99,8 +99,8 @@ public:
   bool  operator==(const Face_handle& fh) const { return fh == pos; }
   bool  operator!=(const Face_handle& fh) const { return fh != pos; }
 
-  bool  operator==(CGAL_NULL_TYPE  CGAL_triangulation_assertion_code(n)) const;
-  bool  operator!=(CGAL_NULL_TYPE n) const;
+  bool  operator==(Nullptr_t  CGAL_triangulation_assertion_code(n)) const;
+  bool  operator!=(Nullptr_t n) const;
   bool  is_empty() const;
   bool  collinear_outside() const;
   bool locate(const Point& t, Locate_type &lt,  int &li);
@@ -664,7 +664,7 @@ is_empty() const
 template < class Gt, class Tds >
 inline bool
 Triangulation_line_face_circulator_2<Gt,Tds>::            
-operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return pos == Face_handle();
@@ -673,7 +673,7 @@ operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
 template < class Gt, class Tds >
 inline bool
 Triangulation_line_face_circulator_2<Gt,Tds>::            
-operator!=(CGAL_NULL_TYPE n) const
+operator!=(Nullptr_t n) const
 {
   CGAL_triangulation_assertion( n == NULL);
   return !(*this == n);
diff --git a/Triangulation_2/test/Triangulation_2/include/CGAL/_test_triangulation_circulators.h b/Triangulation_2/test/Triangulation_2/include/CGAL/_test_triangulation_circulators.h
index a0e7fdc59ff..c52ec9d5c0f 100644
--- a/Triangulation_2/test/Triangulation_2/include/CGAL/_test_triangulation_circulators.h
+++ b/Triangulation_2/test/Triangulation_2/include/CGAL/_test_triangulation_circulators.h
@@ -45,7 +45,7 @@ _test_circulators( const Tr &T )
     {
       vc0 = vc = T.incident_vertices( vit, vit->face() );
       if( !vc.is_empty()){
-	if( vc != CGAL_NULL){
+	if( vc != NULL){
 	  do {
 	    vc++; nvi++;
 	  } while (vc != vc0);
@@ -54,7 +54,7 @@ _test_circulators( const Tr &T )
       //test operator --()
        vc0 = vc = T.incident_vertices( vit, vit->face() );
       if( !vc.is_empty()){
-	if( vc != CGAL_NULL){
+	if( vc != NULL){
 	  do {
 	    vc--; nvi_r++;
 	  } while (vc != vc0);
diff --git a/Triangulation_3/include/CGAL/Delaunay_triangulation_3.h b/Triangulation_3/include/CGAL/Delaunay_triangulation_3.h
index 0a0e89fd1ad..1cb2d942239 100644
--- a/Triangulation_3/include/CGAL/Delaunay_triangulation_3.h
+++ b/Triangulation_3/include/CGAL/Delaunay_triangulation_3.h
@@ -582,15 +582,15 @@ template <class DelaunayTriangulation_3>
 class Delaunay_triangulation_3<Gt, Tds>::Vertex_remover {
   typedef DelaunayTriangulation_3 Delaunay;
 public:
-  typedef CGAL_NULL_TYPE Hidden_points_iterator;
+  typedef Nullptr_t Hidden_points_iterator;
 
   Vertex_remover(Delaunay &tmp_) : tmp(tmp_) {}
 
   Delaunay &tmp;
 
   void add_hidden_points(Cell_handle) {}
-  Hidden_points_iterator hidden_points_begin() { return CGAL_NULL; }
-  Hidden_points_iterator hidden_points_end() { return CGAL_NULL; }
+  Hidden_points_iterator hidden_points_begin() { return NULL; }
+  Hidden_points_iterator hidden_points_end() { return NULL; }
 
   Bounded_side side_of_bounded_circle(const Point &p, const Point &q,
     const Point &r, const Point &s, bool perturb = false) const {
diff --git a/Triangulation_3/include/CGAL/Triangulation_ds_circulators_3.h b/Triangulation_3/include/CGAL/Triangulation_ds_circulators_3.h
index 3602976c42b..da4b8009663 100644
--- a/Triangulation_3/include/CGAL/Triangulation_ds_circulators_3.h
+++ b/Triangulation_3/include/CGAL/Triangulation_ds_circulators_3.h
@@ -146,13 +146,13 @@ public:
     return ch != pos;
   }
 
-  bool operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(n)) const
+  bool operator==(Nullptr_t CGAL_triangulation_assertion_code(n)) const
   {
     CGAL_triangulation_assertion( n == NULL);
     return pos == Cell_handle();
   }
 
-  bool operator!=(CGAL_NULL_TYPE n) const
+  bool operator!=(Nullptr_t n) const
   {
     return ! (*this == n);
   }
@@ -365,13 +365,13 @@ public:
     return ! (*this == ccir);
   }
 
-  bool operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(c)) const
+  bool operator==(Nullptr_t CGAL_triangulation_assertion_code(c)) const
   {
-    CGAL_triangulation_assertion(c == CGAL_NULL);
+    CGAL_triangulation_assertion(c == NULL);
     return pos == Cell_handle();
   }
 
-  bool operator!=(CGAL_NULL_TYPE c) const
+  bool operator!=(Nullptr_t c) const
   {
     return ! (*this == c);
   }
@@ -465,13 +465,13 @@ public:
     return ! (*this == ccir);
   }
 
-  bool operator==(CGAL_NULL_TYPE CGAL_triangulation_assertion_code(c)) const
+  bool operator==(Nullptr_t CGAL_triangulation_assertion_code(c)) const
   {
-    CGAL_triangulation_assertion(c == CGAL_NULL);
+    CGAL_triangulation_assertion(c == NULL);
     return pos == Cell_handle();
   }
 
-  bool operator!=(CGAL_NULL_TYPE c) const
+  bool operator!=(Nullptr_t c) const
   {
     return ! (*this == c);
   }
diff --git a/Visibility_complex_2/include/CGAL/Visibility_complex_2/Polygon_traits.h b/Visibility_complex_2/include/CGAL/Visibility_complex_2/Polygon_traits.h
index 7aeb356938c..27401983746 100644
--- a/Visibility_complex_2/include/CGAL/Visibility_complex_2/Polygon_traits.h
+++ b/Visibility_complex_2/include/CGAL/Visibility_complex_2/Polygon_traits.h
@@ -63,7 +63,7 @@ public:
   void split (Arc_2& tmp, const Bitangent_2& v)
   {
     Point_2 p=v.source_object()==object()?v.source():v.target();
-    if (first == CGAL_NULL) {
+    if (first == NULL) {
       first = object()->vertices_circulator();
       while (*first != p) ++first;
       beyond = first; //++beyond;
@@ -80,7 +80,7 @@ public:
   void split_cw(Arc_2& tmp, const Bitangent_2& v) 
   {
     Point_2 p=v.source_object()==object()?v.source():v.target();
-    if (first == CGAL_NULL) {
+    if (first == NULL) {
       first = object()->vertices_circulator();
       while (*first != p) ++first;
       beyond = first; //++beyond;