diff --git a/Cartesian_kernel/include/CGAL/Cartesian/Circle_3.h b/Cartesian_kernel/include/CGAL/Cartesian/Circle_3.h
index 713dfc08b39..bb2253f4665 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian/Circle_3.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian/Circle_3.h
@@ -278,4 +278,4 @@ CircleC3<R>::operator!=(const CircleC3<R> &t) const
 
 CGAL_END_NAMESPACE
 
-#endif // CGAL_CARTESIAN_CIRCLEC3_H
\ No newline at end of file
+#endif // CGAL_CARTESIAN_CIRCLEC3_H
diff --git a/Cartesian_kernel/include/CGAL/Cartesian/Sphere_3.h b/Cartesian_kernel/include/CGAL/Cartesian/Sphere_3.h
index e758593721c..e064617fe03 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian/Sphere_3.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian/Sphere_3.h
@@ -37,6 +37,7 @@ class SphereC3
   typedef typename R_::Point_3              Point_3;
   typedef typename R_::Vector_3             Vector_3;
   typedef typename R_::Sphere_3             Sphere_3;
+  typedef typename R_::Circle_3             Circle_3;
 
   typedef Triple<Point_3, FT, Orientation>         Rep;
   typedef typename R_::template Handle<Rep>::type  Base;
@@ -128,6 +129,7 @@ public:
   //! precond: ! x.is_degenerate() (when available)
   // Returns R::ON_POSITIVE_SIDE, R::ON_ORIENTED_BOUNDARY or
   // R::ON_NEGATIVE_SIDE
+  bool has_on(const Circle_3 &p) const;
   bool has_on_boundary(const Point_3 &p) const;
   bool has_on_positive_side(const Point_3 &p) const;
   bool has_on_negative_side(const Point_3 &p) const;
@@ -180,6 +182,22 @@ bounded_side(const typename SphereC3<R>::Point_3 &p) const
                                         squared_distance(center(),p)));
 }
 
+template < class R >
+inline
+bool
+SphereC3<R>::
+has_on(const typename SphereC3<R>::Circle_3 &c) const
+{
+  typedef typename SphereC3<R>::Point_3 Point_3;
+  typedef typename SphereC3<R>::FT      FT;
+  Point_3 proj = c.supporting_plane().projection(center());
+  if(!(proj == c.center())) return false;
+  const FT d2 = CGAL::square(center().x() - c.center().x()) +
+                CGAL::square(center().y() - c.center().y()) +
+                CGAL::square(center().z() - c.center().z());
+  return ((squared_radius() - d2) == c.squared_radius());
+}
+
 template < class R >
 inline
 bool
diff --git a/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h b/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h
index 2c03b6379b8..08b3ff380d3 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian/function_objects.h
@@ -3619,6 +3619,7 @@ namespace CartesianKernelFunctors {
     typedef typename K::Plane_3          Plane_3;
     typedef typename K::Triangle_3       Triangle_3;
     typedef typename K::Circle_3         Circle_3;
+    typedef typename K::Sphere_3         Sphere_3;
   public:
     typedef typename K::Bool_type        result_type;
     typedef Arity_tag< 2 >               Arity;
diff --git a/Cartesian_kernel/include/CGAL/Cartesian_converter.h b/Cartesian_kernel/include/CGAL/Cartesian_converter.h
index 631b137168b..b934321da7b 100644
--- a/Cartesian_kernel/include/CGAL/Cartesian_converter.h
+++ b/Cartesian_kernel/include/CGAL/Cartesian_converter.h
@@ -247,6 +247,15 @@ public:
 			a.rep().orientation());
     }
 
+    typename K2::Circle_3
+    operator()(const typename K1::Circle_3 &a) const
+    {
+        typedef typename K2::Circle_3  Circle_3;
+	return Circle_3(operator()(a.center()),
+		        c(a.squared_radius()),
+			c(a.supporting_plane()));
+    }
+
     typename K2::Triangle_3
     operator()(const typename K1::Triangle_3 &a) const
     {