Hi all, Using Boost 1.33.1 serialization library with Micro$oft Visual Studio 2005, I get two minor warnings while compiling the demo_xml.cpp program. They are in boost/serialization/collections_save_imp.hpp. Lines 36 and 37 in the function template save_collection are the culprit, resulting in warnings of the form: warning C4267: 'initializing' : conversion from 'size_t' to 'unsigned int', possible loss of data These are the problem lines: unsigned int count = s.size(); ar << make_nvp("count", const_cast<const unsigned int &>(count)); Changing the "unsigned int" to "size_t" fixes the warnings, like this: size_t count = s.size(); ar << make_nvp("count", const_cast<const size_t &>(count)); Trivial problem, I admit, but warnings are warnings... Cheers, -RSG