I just moved to using boost_asio_0_3_8 because of issues with asio_0_3_7's macro redefinition of FD_SETSIZE. Now, there's no issue with compiling the source, however while linking I get an error saying: undefined reference to `boost::system::get_system_category()' I see from the source that classes "posix_error_category" and "system_error_category" are defined in error_code.cpp (boost_asio_0_3_8/libs/system/src), but there's no actual library (*.so or *.a) to link to. I'm including /path/to/boost_asio_0_3_8 while compiling, but am not doing anything for linking, since all of the code (well almost, since error_code is a cpp file) is .hpp What am I doing wrong? Should I be including anything while linking? regs Vivek