Hi Folks, Strange problem. I have this declared inline in my class header file: friend class boost::serialization::access; template<class Archive> void serialize (Archive &ar, const unsigned int version); { ar & m_name; // std::string } Builds fine, then I move this to my .cpp file and I get a link error. Here is the output from the linker: test.o(.gnu.linkonce.t._ZN5boost13serialization6access9serializeINS_7archive13text_oarchiveEN19test_RT0_j+0x13): In function `void boost::serialization::access::serialize<boost::archive::text_oarchive, Attribute>(boost::archive::text_oarchive&, Attribute&, unsigned)': /usr/include/c++/3.2.2/bits/stl_alloc.h:238: undefined reference to `void Attribute::serialize<boost::archive::text_oarchive>(boost::archive::text_oarchive&, unsigned)' root/abcmn/cmnUtilities/cmnGenericObjects/tests/GenericObjectsTests.o(.gnu.linkonce.t._ZN5boost13serialization6access9serializeINS_7archive13text_oarchiveEN19test_RT0_j+0x13): In function `void boost::serialization::access::serialize<boost::archive::text_iarchive, Attribute>(boost::archive::text_iarchive&, Attribute&, unsigned)': /usr/include/c++/3.2.2/bits/stl_alloc.h:238: undefined reference to `void Attribute::serialize<boost::archive::text_iarchive>(boost::archive::text_iarchive&, unsigned)' collect2: ld returned 1 exit status Any ideas? Thanks, Kauai __________________________________ Do you Yahoo!? Plan great trips with Yahoo! Travel: Now over 17,000 guides! http://travel.yahoo.com/p-travelguide