I have been trying to link the boost::regex library to a DLL (Release build) without success and I really need help. I have learned something new. Hitherto, I have put this line right above my code in one of my header files, i.e., within the "#if !defined()" block that prevents duplicate inclusion: #define BOOST_REGEX_STATIC_LINK This has no effect on the build whatsoever. The resulting DLL is no bigger and the client will not work if you rename boost_regex_vc6_mdi.dll from its place. You get an error message from the client saying that this file is missing. If, however, I place the line above as the very first line in a header file, then, instead, I simply cannot compile and build the project at all. The compile error I am getting states that there are "multiply defined symbols"! I.e., the symbols defined in the library are being defined twice. This is driving me nuts. Thanks for any help. Amittai Aviram amittai@amittai.com