Hi, I came up with a solution that seems to work. It is as simple as adding "const" to the Value template parameter of the iterator_adapter. Then I can have a non- const iterator that always returns const when dereferenced. Unfortunately, the iterator_adapter class has a public member function "base" that returns the underlying iterator. Since I want to prevent public access to the underlying operator, I had to tweak iterator_adapter and make this function protected. Then I want to give access to the base function only to the container adaptor (a map adaptor in my example). Providing the friend access in a generic way is a little bit awkward, as it has to be done through a helper class. Some sample code for this is given below. I have not yet fully explored this solution, I hope I won't face any nasty surprises. Martin #include <boost/iterator/iterator_adaptor.hpp> template<class GetsAccess> class FriendHelper; //non-const Iterator that will be disguised as const iterator, //only ContainerAdaptor will get access to the real iterator template <class Iterator, class ContainerAdaptor> class const_iter :public boost::iterator_adaptor< const_iter<Iterator, ContainerAdaptor>, //a std iterator Iterator, //the type that the iterator points to, but constified const typename Iterator::value_type > { public: const_iter() : const_iter::iterator_adaptor_() {} explicit const_iter(const Iterator& p) : const_iter::iterator_adaptor_(p) {} protected: //provide access to the underlying iterator to the //ContainerAdaptor friend class FriendHelper< ContainerAdaptor >; const_iter<Iterator, ContainerAdaptor> const& base() const { return base(); } }; //the ContainerAdaptor gets access to the constiter base function template<class ContainerAdaptor> class FriendHelper { typedef typename ContainerAdaptor::constiter_type constiter_type; public: constiter_type const& base( const constiter_type& constit ) { return constit.base(); } }; //sketch of an adaptor to map class mymap{ private: friend class FriendHelper<mymap>; typedef std::map<int, int> mymap_type; typedef const_iter<mymap_type::iterator, mymap > constiter_type; public: void dosomething() { mymap_type testmap; constiter_type mit(testmap.begin()); //access the underlying operator through FriendHelper FriendHelper<mymap>().base(mit); } };