I've just checked in changes to Win32 implementations of the mutex and recursive_mutex classes. They now use a Win32 critical section instead of a mutex whenever possible for the normal and try_ variations, though not for the timed_ variations. These are changes that were started on the mutex classes quite some time back on the thread_dev branch; I've finished the changes and applied them to the recursive_mutex classes as well. In addition, the thread_dev branch has code that allows a mutex to be named, which allows it to be shared between two or more processes. This change was begun by Bill Kempf, but is only implemented for Win32. Any suggestions about the best way to add this feature to the pthreads and MPTasks implementations? Mike