diff --git a/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modularizable.tex b/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modularizable.tex
index b7e9fa01b0b..2eaea753394 100644
--- a/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modularizable.tex
+++ b/Modular_arithmetic/doc_tex/Modular_arithmetic_ref/Modularizable.tex
@@ -5,28 +5,35 @@
 An algebraic structure is called \ccRefName, if there is a suitable mapping 
 into an algebraic structure which is based on the type \ccc{CGAL::Residue}. 
 For scalar types, e.g. Integers, this mapping is just the canonical homomorphism 
-into the type \ccc{CGAL::Residue}. For compound types, e.g. Polynomials, 
+into the type \ccc{CGAL::Residue} with respect to the current prime. 
+For compound types, e.g. Polynomials, 
 the mapping is applied to the coefficients of the compound type. 
 
 The mapping is provided via \ccc{CGAL::Modular_traits<Modularizable>}, 
 being a model of \ccc{ModularTraits}.
 
+Note that types representing rationals, or types which do have some notion 
+of denominator, are not \ccc{Modularizable}. 
+This is due to the fact that the denominator may be zero modulo the prime, 
+which can not be represented.  
+
+%\ccRefIdfierPage{CORE::BigRat}\\
+%\ccRefIdfierPage{CGAL::Gmpq}\\
+%\ccRefIdfierPage{leda::rational}\\
+%\ccRefIdfierPage{mpq_class}\\
+%\ccRefIdfierPage{CGAL::Quotient<NT>}\\
+
 \ccHasModels
 
 \ccRefIdfierPage{int}\\
 \ccRefIdfierPage{long}\\
 \ccRefIdfierPage{CORE::BigInt}\\
-\ccRefIdfierPage{CORE::BigRat}\\
 \ccRefIdfierPage{CGAL::Gmpz}\\
-\ccRefIdfierPage{CGAL::Gmpq}\\
 \ccRefIdfierPage{leda::integer}\\
-\ccRefIdfierPage{leda::rational}\\
 \ccRefIdfierPage{mpz_class}\\
-\ccRefIdfierPage{mpq_class}\\
 
-\ccRefIdfierPage{CGAL::Quotient<NT>}, depends on template argument.\\ 
 \ccRefIdfierPage{CGAL::Lazy_exact_nt<NT>}, depends on template argument.\\ 
-\ccRefIdfierPage{CGAL::Sqrt_extension<NT,ROOT>}, depends on template arguments.\\ 
+\ccRefIdfierPage{CGAL::Sqrt_extension<NT,ROOT>}, depends on template arguments.\\
 \ccRefIdfierPage{CGAL::Polynomial<Coeff>}, depends on template argument.\\ 
 
 \ccSeeAlso
diff --git a/Modular_arithmetic/test/Modular_arithmetic/Modular_traits.cpp b/Modular_arithmetic/test/Modular_arithmetic/Modular_traits.cpp
index 16c5622e306..726892696e8 100644
--- a/Modular_arithmetic/test/Modular_arithmetic/Modular_traits.cpp
+++ b/Modular_arithmetic/test/Modular_arithmetic/Modular_traits.cpp
@@ -11,7 +11,6 @@
 #include <CGAL/Modular_traits.h>
 #include <CGAL/Sqrt_extension.h>
 #include <CGAL/Polynomial.h>
-#include <CGAL/Quotient.h>
 #include <CGAL/Lazy_exact_nt.h>
 //#include <CGAL/MP_Float.h>
  
@@ -23,14 +22,11 @@
 
 #ifdef CGAL_USE_CORE
 #include <CGAL/CORE_BigInt.h>
-#include <CGAL/CORE_BigRat.h>
 #endif // CGAL_USE_CORE
 
 #ifdef CGAL_USE_GMP
 #include <CGAL/Gmpz.h>
-#include <CGAL/Gmpq.h>
 #include <CGAL/mpz_class.h>
-#include <CGAL/mpq_class.h>
 #endif // CGAL_USE_GMP
 
 
@@ -80,28 +76,20 @@ int main()
    
 #ifdef CGAL_USE_LEDA
     test_modular_traits<leda::integer>();
-    test_modular_traits<leda::rational>();
     test_modular_traits<CGAL::Polynomial< leda::integer > >();
-    test_modular_traits<CGAL::Polynomial< leda::rational > >();
-    test_modular_traits<CGAL::Quotient< leda::integer > >();
     test_modular_traits<CGAL::Lazy_exact_nt< leda::integer > >();
     test_modular_traits<CGAL::Sqrt_extension< leda::integer , leda::integer > >();
 #endif
 #ifdef CGAL_USE_CORE
     test_modular_traits<CORE::BigInt>();
-    test_modular_traits<CORE::BigRat>();
     test_modular_traits<CGAL::Polynomial< CORE::BigInt > >();
-    test_modular_traits<CGAL::Polynomial< CORE::BigRat > >();
-    test_modular_traits<CGAL::Quotient< CORE::BigInt > >();
     test_modular_traits<CGAL::Lazy_exact_nt< CORE::BigInt > >();
     test_modular_traits<CGAL::Sqrt_extension< CORE::BigInt , CORE::BigInt > >();
 #endif
 
 #ifdef CGAL_USE_GMP
     test_modular_traits<CGAL::Gmpz>();
-    test_modular_traits<CGAL::Gmpq>();
     test_modular_traits< mpz_class >();
-    test_modular_traits< mpq_class >();
 #endif
     
     // test Sqrt_extension
@@ -115,15 +103,6 @@ int main()
     assert(
         !CGAL::Modular_traits<CGAL::Polynomial<double> >
         ::Is_modularizable::value);
-    
-    // test Quotient
-    test_modular_traits<CGAL::Quotient< int > >();
-    assert(
-        !CGAL::Modular_traits<CGAL::Quotient<double> >
-        ::Is_modularizable::value);
-    assert(
-        !CGAL::Modular_traits<CGAL::Quotient<CGAL::Polynomial<int> > >
-        ::Is_modularizable::value);
 
     // test_modular_traits<CGAL::MP_Float >();
     
diff --git a/Number_types/include/CGAL/CORE_BigRat.h b/Number_types/include/CGAL/CORE_BigRat.h
index d51a49620b4..0dd1e92f277 100644
--- a/Number_types/include/CGAL/CORE_BigRat.h
+++ b/Number_types/include/CGAL/CORE_BigRat.h
@@ -26,9 +26,6 @@
 #include <CGAL/CORE_coercion_traits.h>
 #include <CGAL/CORE_Expr.h> // used for To_interval-functor
 
-#include <CGAL/Residue.h>
-#include <CGAL/Modular_traits.h>
-
 //#if defined(CGAL_CORE_BIGRAT_NUMER_DENOM_ARE_MEMBERS)
 //  #define CGAL_CORE_NUMERATOR(X) ((X).numerator())
 //  #define CGAL_CORE_DENOMINATOR(X) ((X).denominator())
@@ -154,34 +151,6 @@ public:
     };
 };
 
-/*! \ingroup NiX_Modular_traits_spec
- *  \brief a model of concept ModularTraits, 
- *  specialization of NiX::Modular_traits. 
- */
-template<>
-class Modular_traits< ::CORE::BigRat > {
-  typedef ::CORE::BigInt Integer;
-  typedef Modular_traits<Integer> MT_int;
-public:
-  typedef ::CORE::BigRat NT;
-  typedef ::CGAL::Tag_true Is_modularizable;
-  typedef CGAL::Residue Residue_type;
-  struct Modular_image{
-    Residue_type operator()(const NT& rat){
-      MT_int::Modular_image int_mod;
-      Residue_type num = int_mod(CGAL_CORE_NUMERATOR(rat));
-      Residue_type den = int_mod(CGAL_CORE_DENOMINATOR(rat));
-      return num/den;
-    }
-  };   
-  struct Modular_image_representative{
-    NT operator()(const Residue_type& x){
-      return NT(x.get_value());
-    }
-  };    
-};
-
-
 template <class F>
 class Output_rep< ::CORE::BigRat, F> {
     const ::CORE::BigRat& t;
diff --git a/Number_types/include/CGAL/Gmpq.h b/Number_types/include/CGAL/Gmpq.h
index a2de7d96e61..34486fa7097 100644
--- a/Number_types/include/CGAL/Gmpq.h
+++ b/Number_types/include/CGAL/Gmpq.h
@@ -24,7 +24,6 @@
 #include <CGAL/number_type_basic.h>
 #include <CGAL/Gmpz.h>
 #include <CGAL/Gmp_coercion_traits.h>
-#include <CGAL/Modular_traits.h>
 
 CGAL_BEGIN_NAMESPACE
 
@@ -133,33 +132,6 @@ public:
     };
 };
 
-/*! \ingroup NiX_Modular_traits_spec
- *  \brief a model of concept ModularTraits, 
- *  specialization of NiX::Modular_traits. 
- */
-template<>
-class Modular_traits< Gmpq > {
-public:
-  typedef Gmpq NT;
-  typedef CGAL::Tag_true Is_modularizable;
-  typedef Residue Residue_type;
-
-  struct Modular_image{
-    Residue_type operator()(const NT& a){
-      Gmpz num(a.numerator()   % Residue::get_current_prime() );
-      Gmpz den(a.denominator() % Residue::get_current_prime() );
-      Residue num_m (CGAL::Residue(int(mpz_get_si(num.mpz()))));
-      Residue den_m (CGAL::Residue(int(mpz_get_si(den.mpz()))));
-      return num_m / den_m; 
-    }
-  };
-  struct Modular_image_representative{
-    NT operator()(const Residue_type& x){
-      return NT(x.get_value());
-    }
-  };    
-};
-
 CGAL_END_NAMESPACE
 
 //since types are included by Gmp_coercion_traits.h:
diff --git a/Number_types/include/CGAL/Quotient.h b/Number_types/include/CGAL/Quotient.h
index 225c8a8fc30..89c572d0716 100644
--- a/Number_types/include/CGAL/Quotient.h
+++ b/Number_types/include/CGAL/Quotient.h
@@ -42,7 +42,6 @@
 #include <CGAL/Kernel/mpl.h>
 
 #include <boost/operators.hpp>
-#include <CGAL/Modular_traits.h>
 
 CGAL_BEGIN_NAMESPACE
 
@@ -869,61 +868,6 @@ public:
     };
 };
 
-//fwd 
-class Residue;
-
-namespace CGALi{
-
-template<typename RT, typename TAG>
-struct Quotient_modular_traits_base{
-  typedef Quotient<RT> NT;
-  typedef ::CGAL::Tag_false Is_modularizable;
-  typedef ::CGAL::Null_functor Residue_type;
-  typedef ::CGAL::Null_functor Modular_image;  
-  typedef ::CGAL::Null_functor Modular_image_representative;    
-};
-
-template<typename RT>
-class Quotient_modular_traits_base<RT,CGAL::Tag_true>{ 
-public:
-  typedef Quotient<RT> NT;
-  typedef CGAL::Tag_true Is_modularizable;
-  typedef Residue Residue_type;
-
-  struct Modular_image{
-    Residue_type operator()(const NT& a){
-      typedef CGAL::Modular_traits<RT> MT_RT;
-      typename MT_RT::Modular_image modular_image;
-      typename MT_RT::Residue_type num(modular_image(a.numerator()));
-      typename MT_RT::Residue_type den(modular_image(a.denominator()));
-      return num / den; 
-    }
-  };
-  struct Modular_image_representative{
-    NT operator()(const Residue_type& x){
-      return NT(x.get_value());
-    }
-  };    
-};
-
-template <typename RT>
-struct Quotient_is_modularizable{
-private:
-  typedef typename Modular_traits<RT>::Residue_type Residue_type;
-  typedef Algebraic_structure_traits<Residue_type> AST;
-  typedef typename AST::Algebraic_category Algebraic_category;
-  typedef CGAL::is_same_or_derived<Algebraic_category,CGAL::Field_tag> Is_field;
-public:
-  typedef CGAL::Boolean_tag<Is_field::value> Type;
-};
-
-} // namespace CGALi
-
-template <typename RT> 
-class Modular_traits<Quotient<RT> >
-  :public CGALi::Quotient_modular_traits_base
-    <RT,typename CGALi::Quotient_is_modularizable<RT>::Type>{};
-
 CGAL_END_NAMESPACE
 
 #endif  // CGAL_QUOTIENT_H
diff --git a/Number_types/include/CGAL/leda_rational.h b/Number_types/include/CGAL/leda_rational.h
index 8995065d31e..9321f9a05fe 100644
--- a/Number_types/include/CGAL/leda_rational.h
+++ b/Number_types/include/CGAL/leda_rational.h
@@ -31,9 +31,6 @@
 #include <CGAL/leda_coercion_traits.h>
 #include <CGAL/Interval_nt.h>
 
-#include <CGAL/Residue.h>
-#include <CGAL/Modular_traits.h>
-
 #include <CGAL/Needs_parens_as_product.h>
 
 #include <utility>
@@ -202,32 +199,6 @@ public:
     };
 };
 
-// Modular_traits
-template<>
-class Modular_traits< ::leda::rational > {
-  typedef ::leda::integer Integer;
-  typedef CGAL::Modular_traits<Integer> MT_int;
-public:
-  typedef ::leda::rational NT;
-  typedef ::CGAL::Tag_true Is_modularizable;
-  typedef CGAL::Residue Residue_type;
-
-  struct Modular_image{
-    Residue_type operator()(const NT& rat){
-      MT_int::Modular_image int_mod;
-      Residue_type num = int_mod(rat.numerator());
-      Residue_type den = int_mod(rat.denominator());
-      return num/den;
-    }
-  };
-  struct Modular_image_representative{
-    NT operator()(const Residue_type& x){
-      return NT(x.get_value());
-    }
-  };    
-};
-
-
 template <class F>
 class Output_rep< leda_rational, F> {
     const leda_rational& t;
diff --git a/Number_types/include/CGAL/mpq_class.h b/Number_types/include/CGAL/mpq_class.h
index 6a9bf26e03f..6e80aa7ca52 100644
--- a/Number_types/include/CGAL/mpq_class.h
+++ b/Number_types/include/CGAL/mpq_class.h
@@ -284,31 +284,6 @@ public:
     };
 };
 
-template<>
-class Modular_traits< mpq_class > {
-public:
-  typedef mpq_class NT;
-  typedef CGAL::Tag_true Is_modularizable;
-  typedef Residue Residue_type;
-
-  struct Modular_image{
-    Residue_type operator()(const mpq_class& a){
-      typedef Fraction_traits<mpq_class> FT;
-      mpz_class num, den;  
-      FT::Decompose()(a,num,den);
-      mpz_class prime(Residue::get_current_prime());
-      CGAL::Residue num_m(int(mpz_get_si(CGAL::mod(num,prime).get_mpz_t())));
-      CGAL::Residue den_m(int(mpz_get_si(CGAL::mod(den,prime).get_mpz_t())));
-      return num_m/den_m;
-    }
-  };
-  struct Modular_image_representative{
-    NT operator()(const Residue_type& x){
-      return NT(x.get_value());
-    }
-  };    
-};
-
 CGAL_END_NAMESPACE
 
 #undef CGAL_CHECK_GMP_EXPR