Ok, I've determined that the memory leak I was seeing is real, atleast in vc7.1. The boost::detail::sp_counted_base_impl<P,D> held by a serialization loaded shared_ptr never gets deleted. This is due to boost::serialization::load_construct_data setting weak_count to 0. When the sp_counted_base::weak_release() gets called new_weak_count is -1 so destruct is not called. A fix that works for my application, is to comment out the line: shared_ptr_access::weak_count(*t) = 0; in template<class Archive, class P, class D> inline void load_construct_data( Archive & ar, boost::detail::sp_counted_base_impl<P, D> * t, const unsigned int /* file_version */ The following was used to reproduce the problem in vc7.1. // SerializationSharedPtrTest.cpp : Defines the entry point for the console application. // #define CRTDBG_MAP_ALLOC #include <stdlib.h> #include <crtdbg.h> struct Checker { Checker() { _CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_CHECK_ALWAYS_DF | _CRTDBG_LEAK_CHECK_DF ); } }; Checker lChecker; #include <boost/serialization/shared_ptr.hpp> #include <boost/archive/text_oarchive.hpp> #include <boost/archive/text_iarchive.hpp> #include <fstream> typedef std::string tName; class PointedToClass { int mInt; friend class boost::serialization::access; template< class Archive > void serialize( Archive &ar, unsigned int version ) { ar & boost::serialization::make_nvp( "Int", mInt ); } public: ~PointedToClass(){} PointedToClass():mInt(123){} PointedToClass( int aInt ):mInt( aInt){} PointedToClass( const PointedToClass& aRhs ):mInt(aRhs.mInt){} }; typedef boost::shared_ptr< PointedToClass > tPtr; int main( int argc, char* argv[] ) { { std::ofstream lOut( "SomeClass.archive", std::ios_base::out | std::ios_base::trunc ); if( lOut.good() ) { boost::archive::text_oarchive oa( lOut ); tPtr lPtr( new PointedToClass(456) ); oa << boost::serialization::make_nvp( "Ptr" , lPtr ); } } { std::ifstream lIn( "SomeClass.archive" ); tPtr lPtr; if( lIn.good() ) { boost::archive::text_iarchive ia( lIn ); ia >> boost::serialization::make_nvp( "Ptr" , lPtr ); } } return 0; }