I'm linking to boost programming options under windows. I get the following linker error: miind.obj : error LNK2001: unresolved external symbol "public: static unsigned int const boost::program_options::options_description::m_default_line_length" I am using the BoostPro installer version for boost 1.47 under windows XP using Visual Studio 10. I link against: boost_program_options-vc100-mt-gd-1_47.lib in Debug mode. If I don't link against it I get a lot more missing symbols, so it's not simply a matter of forgetting to the boost program options library. The problem occurs in the Debug and Release version. The same code compiles under Linux. Marc