The file is_abstract.hpp in serialization18 and is_abstract.hpp in type traits library (in cvs) have conflict definitions of "boost::is_abstract". May Ramey fix this. For now, I just comment out the latter in order to use serialization18. In addition, I am confused with the ".ipp" files in libs/serialization/src/ in serialization18. It is strange to write #include <libs/serialization/src/basic_binary_oprimitive.ipp> // for serialization18 in user code instead of #include <boost/serialization/basic_binary_oprimitive.ipp> // for serialization17 I wonder why these files can not be just named ".hpp" Ramey, when will we see the serialization library in boost cvs, please? Thank you:)