I think I've found a bug in program_options. #define _SECURE_SCL 0 on Visual Studio 2005 causes program_options to crash in store(). I used boost from CVS. Below is an example. Thanks for an awesome library! Roger -- #define _SECURE_SCL 0 #include namespace po = boost::program_options; int main(int argc, char* argv[]) { po::options_description desc("Allowed Options"); desc.add_options() ("help", "produce help message") ; po::variables_map vm; po::store(po::parse_command_line(argc, argv, desc), vm); po::notify(vm); return 0; }