Status Currently, only the LinuxThreads implementation of POSIX threads have been tested (as in GLIBC 2.2.5). The system I've mainly used for developing the POSIX interface is a Debian GNU/Linux 3.0 (woody) on a dual CPU system. I'd be interresting to test it against other POSIX implementations, especially native ones, but unfortunately I don't have easy access to such other systems (volunteers?). The library is also tested semi-succesfully on a Cygwin platform on top of a WindowsXP box. The when_exit.cc test program gives a core dump, and cancel_cleanup.cc fails too. I've used GCC 3.0.4 and 2.95.4, as well as Intel'stm C++ compiler too. Everything works with a few minor exceptions. Notice, when compiling with GCC 2.95.4 and Intel's C++ compiler, against the LinuxThreads implementation in GLIBC 2.2.5, the barrier, rwlock, and spinlock are not supported per default. To enable these with GCC 2.95.4, the preprocessor symbol _GNU_SOURCE must defined. This is easily done by doing ./configure CXX="gcc -D_GNU_SOURCE" ... I have implementet support for C Threads (as found in GNU/Hurd) too, but haven't tested it yet. C threads are really light-weight, and only support the absolute miminmal set of concepts: condition , mutex , and thread . On the other hand, they are well integrated and used in the GNU Mach kernel and have good performance. Win32API threads are interresting too, in that they are completly different (as far as I know at least). Any other kind of API (is there any?) would be interresting too. I know MacOS used to have it's own API, but I guess from MacOSX and upward, they use a POSIX API.