Hello This is my last problem with the BSL but the most important one (because there is no workaround). I am trying to serialize a class (whose name is "ClassSpecification") which has a std::vector of pointers. The code for serializing the class the pointer refer to (MemberVariableSpecification) is written and instantiated correctly. However I cannot correctly serialize the std::vector. It fails with a message complaining about: C:/Boost/include/boost-1_33_1/boost/archive/detail/iserializer.hpp:115: error: incomplete type `boost::serialization::extended_type_info_null<std::vector<MemberVariableSpecification*, std::allocator<MemberVariableSpecification*> > >' used in nested name specifier I do not understand why I need an extended_type_info for this vector. I sure need it for the class the pointers refer to (and I did specify it), but the std::vector itself is serialized as such, not as a pointer. Why do I get this error ??? Can you please check the attached code and help me? Thanks Jean-Noël Ps: using gcc 3.4.2