Hi: Following the previous message, I've altered the command line used to: Bjam toolset=msvc stage -SZLIB_SOURCE="c:\progrma files\zlib\" This still doesn't find the zlib.h file which is in c;\program files\zlib. Can someone give me a command line under windows that builds this successfully, or tell me what is going wrong, as I appear to have followed instructions in the IO streams docs. Cheers Sean.