The last bullet item on page libs/locale/doc/html/index.html says: Many standard libraries provide only the C and POSIX locales, thus GCC supports localization only under Linux. On all other platforms, attempting to create locales other than "C" or "POSIX" would fail. Actually, locale("") works on most platforms, including PC-BSD and Open Solaris, so needs to be added to the above list of locales that do work. Look at the trunk filesystem regression first test, "locale_info", and click on the Pass link to see the output. locale("") is working pretty much across the board, even on the Darwin tests. Mac OS X is of particular interest because by default locale("") does fall, and the Apple folks have said in the past that they won't fix it. It fails on my Mac mini in the default configuration. Presumably the Darwin regression test machine has something beyond the default configuration. Also, would it be possible to use locales from the Apache library? See http://stdcxx.apache.org/doc/stdlibref/locale.html#Table%C2%A021 --Beman