When started form a Windows Commandline (cmd.exe) bjam tries to create existing directories and of curse failes to do so! For example when building boost::thread: ------------------------------------ ...found 205 targets... ...updating 20 targets... MkDir1 ..\..\..\bin\boost\libs\thread\build\boost_thread.dll\cw\\threading-multi Ein Unterverzeichnis oder eine Datei mit dem Namen "..\..\..\bin\boost\libs\thre ad\build\boost_thread.dll\cw\\threading-multi" existiert bereits. mkdir "..\..\..\bin\boost\libs\thread\build\boost_thread.dll\cw\\threading- multi" ...failed MkDir1 ..\..\..\bin\boost\libs\thread\build\boost_thread.dll\cw\\threa ding-multi... ------------------------------------ (the german error-msg means "directory or file "..." allready exists") As this causes targets to be skipped this is getting pretty annoying ... As far as i understand the root of the problem is that the nativ "mkdir" on Win32 does not take any options to be quiet if the directory exists ("-p" on Unix). It looks like allyourbase.jam tries to address this in the MkDir rule, but fails to. Bertolt PS: I have tried to post this in gmane.comp.lib.boost.build but i always got mail that i should join <jamboost@yahoogroups.com>!