Try ///////////////////////// without effect //////////////////////////////////// template void CSerTest::serialize<boost::archive::xml_oarchive>(boost::archive::xml_oarchive&, const unsigned int ); // add const !!! Also a couple of unrelated suggestions: // Class.hpp // the following will bloat your code even whenever you use this header even when not actually using // xml_?archives - so better not to include it here: //#include <boost/archive/xml_oarchive .hpp> //#include <boost/archive/xml_iarchive.hpp> .... // main.cpp #include <fstream> #include "Class.hpp" #include <boost/archive/xml_oarchive .hpp> #include <boost/archive/xml_iarchive.hpp> ///////////////////////// without effect //////////////////////////////////// template void CSerTest::serialize<boost::archive::xml_oarchive>(boost::archive::xml_oarchive&, const unsigned int ); // "const" added!! to match template in declaration int main() { const CSerTest instance; // check rationale on this. std::ofstream ofs( "out_file.txt" ); boost::archive::xml_oarchive oxa( ofs ); oxa << BOOST_SERIALIZATION_NVP(instance); } **** this should work. Robert Ramey