diff --git a/Installation/include/CGAL/atomic.h b/Installation/include/CGAL/atomic.h
index da0a5c1c0a2..c9b6969b132 100644
--- a/Installation/include/CGAL/atomic.h
+++ b/Installation/include/CGAL/atomic.h
@@ -17,34 +17,21 @@
 
 #ifdef CGAL_HAS_THREADS
 
-#  ifdef CGAL_CAN_USE_CXX11_ATOMIC
 #    include <atomic>
-#    define CGAL_ATOMIC_NS std
-#  else // not CGAL_CAN_USE_CXX11_ATOMIC
-#    if BOOST_VERSION >= 105300
-#      include <boost/atomic.hpp>
-#      define CGAL_ATOMIC_NS boost
-#    else // BOOST_VERSION < 105300
-#      define CGAL_NO_ATOMIC "Boost.Atomic was introduced in Boost-1.53".
-#    endif // BOOST_VERSION < 105300
-#  endif // not CGAL_CAN_USE_CXX11_ATOMIC
 
-#  ifndef CGAL_NO_ATOMIC
-   namespace CGAL {
-     namespace cpp11 {
-       using CGAL_ATOMIC_NS ::atomic;
+namespace CGAL {
+namespace cpp11 {
+using std::atomic;
 
-       using CGAL_ATOMIC_NS ::memory_order_relaxed;
-       using CGAL_ATOMIC_NS ::memory_order_consume;
-       using CGAL_ATOMIC_NS ::memory_order_acquire;
-       using CGAL_ATOMIC_NS ::memory_order_release;
-       using CGAL_ATOMIC_NS ::memory_order_acq_rel;
-       using CGAL_ATOMIC_NS ::memory_order_seq_cst;
+using std::memory_order_relaxed;
+using std::memory_order_consume;
+using std::memory_order_acquire;
+using std::memory_order_release;
+using std::memory_order_acq_rel;
+using std::memory_order_seq_cst;
 
-       using CGAL_ATOMIC_NS ::atomic_thread_fence;
-     }
-   }
-#  endif // CGAL_ATOMIC_NS
+using std::atomic_thread_fence;
+} }
 #else
 #  define CGAL_NO_ATOMIC "No atomic because CGAL_NO_THREADS is defined."
 #endif // CGAL_HAS_THREADS
diff --git a/Installation/include/CGAL/config.h b/Installation/include/CGAL/config.h
index 6294f2ca523..39d1b5d4b3a 100644
--- a/Installation/include/CGAL/config.h
+++ b/Installation/include/CGAL/config.h
@@ -127,16 +127,6 @@
 #include <boost/config.hpp>
 #include <boost/version.hpp>
 
-// Hack: Boost<1.55 does not detect correctly the C++11 features of ICC.
-// We declare by hand two features that we need (variadic templates and
-// rvalue references).
-#if defined(__INTEL_COMPILER) && defined(__GXX_EXPERIMENTAL_CXX0X__)
-#  undef BOOST_NO_VARIADIC_TEMPLATES
-#  undef BOOST_NO_CXX11_VARIADIC_TEMPLATES
-#  undef BOOST_NO_RVALUE_REFERENCES
-#  undef BOOST_NO_CXX11_RVALUE_REFERENCES
-#endif
-
 #include <CGAL/version.h>
 
 //----------------------------------------------------------------------//
@@ -400,25 +390,6 @@ using std::max;
 #  endif
 #endif
 
-#if __has_feature(cxx_thread_local) || \
-    ( (__GNUC__ > 0) && __cplusplus >= 201103L ) || \
-    ( _MSC_VER >= 1900 )
-// see also Installation/cmake/modules/config/support/CGAL_test_cpp_version.cpp
-#define CGAL_CAN_USE_CXX11_THREAD_LOCAL
-#endif
-
-#if (__has_include(<mutex>) && __cplusplus >= 201103L ) | \
-    ( (__GNUC__ > 0) && __cplusplus >= 201103L ) || \
-    ( _MSC_VER >= 1700 )
-#define CGAL_CAN_USE_CXX11_MUTEX
-#endif
-
-#if (__has_include(<atomic>) && __cplusplus >= 201103L ) || \
-    ( (__GNUC__ > 0) && __cplusplus >= 201103L ) || \
-    ( _MSC_VER >= 1700 )
-#define CGAL_CAN_USE_CXX11_ATOMIC
-#endif
-
 #ifndef CGAL_HAS_THREADS
   namespace CGAL { inline bool is_currently_single_threaded(){ return true; } }
 #elif __has_include(<sys/single_threaded.h>)
diff --git a/Installation/include/CGAL/mutex.h b/Installation/include/CGAL/mutex.h
index e7c58beec27..48421e667c7 100644
--- a/Installation/include/CGAL/mutex.h
+++ b/Installation/include/CGAL/mutex.h
@@ -13,14 +13,8 @@
 #include <CGAL/config.h>
 
 #ifdef CGAL_HAS_THREADS
-#ifdef CGAL_CAN_USE_CXX11_MUTEX
 #include <mutex>
 #define CGAL_MUTEX std::mutex
 #define CGAL_SCOPED_LOCK(M) std::unique_lock<std::mutex> scoped_lock(M)
-#else
-#include <boost/thread/mutex.hpp>
-#define CGAL_MUTEX boost::mutex
-#define CGAL_SCOPED_LOCK(M) boost::mutex::scoped_lock scoped_lock(M)
-#endif
 #endif
 #endif // CGAL_MUTEX_H
diff --git a/Number_types/include/CGAL/Mpzf.h b/Number_types/include/CGAL/Mpzf.h
index 60034bb3896..b1b023a1058 100644
--- a/Number_types/include/CGAL/Mpzf.h
+++ b/Number_types/include/CGAL/Mpzf.h
@@ -112,16 +112,9 @@
 #if !defined(CGAL_HAS_THREADS)
 #define CGAL_MPZF_THREAD_LOCAL
 #define CGAL_MPZF_TLS
-#elif defined(CGAL_CAN_USE_CXX11_THREAD_LOCAL)
+#else
 #define CGAL_MPZF_THREAD_LOCAL thread_local
 #define CGAL_MPZF_TLS thread_local
-#elif defined(_MSC_VER)
-#define CGAL_MPZF_THREAD_LOCAL __declspec(thread)
-#define CGAL_MPZF_TLS
-#else
-#define CGAL_MPZF_THREAD_LOCAL __thread
-#define CGAL_MPZF_TLS
-// Too bad for the others
 #endif
 namespace CGAL {
 namespace Mpzf_impl {
@@ -162,7 +155,6 @@ template <class T, class = void> struct pool2 {
   static T& ptr(T t) { t -= extra+1; return *reinterpret_cast<T*>(t); }
 };
 
-#if defined(CGAL_CAN_USE_CXX11_THREAD_LOCAL)
 template <class T, class = void> struct pool3 {
   static T pop() { T ret = data(); data() = ptr(data()); return ret; }
   static void push(T t) { ptr(t) = data(); data() = t; }
@@ -185,7 +177,6 @@ template <class T, class = void> struct pool3 {
   }
   static T& ptr(T t) { t -= extra+1; return *reinterpret_cast<T*>(t); }
 };
-#endif
 
 // No caching
 template <class T, class = void> struct no_pool {