Dear Volodya, The version of Boost.program_options I am using throws lots of informative exceptions to indicate precisely what has gone wrong. The exception is where an incorrect argument to an option has been supplied e.g. --some_arg "abc" where --some_arg 0.6 is expected. The error message is annoyingly non-descript and it can be difficult to figure out which particular optional argument has been mis-specified. This imprecision is because when program_options::validation_error is being thrown, it is not clear which option is being parsed. Could I suggest that this particular exception is caught in: void store(const parsed_options& options, variables_map& xm, bool utf8) and the option context added back in (and the same exception type re-thrown): void store(const parsed_options& options, variables_map& xm, bool utf8) { ... // First, convert/store all given options for ( size_t i = 0; i < options.options.size(); ++i ) { const string& name = options.options[i].string_key; try { ... } catch ( validation_error& e ) { throw validation_error("[--" + name + "]: " + e.what()); } } ... } What do you think? Leo Goodstadt MRC Functional Genetics Unit University of Oxford