I've implemented some limited thread-safe extensions to the boost signals library for my own use. My signal_mt, connection_mt, and scoped_connection_mt classes provide some basic multi-threaded functionality, although I certainly don't pretend they are particularly mature or elegant. For the curious, my thread-safe extensions can be found at: http://braddock.com/~braddock/signals_mt/ Included is some unit testing code which provides some usage examples and reasonably good code coverage (although it is not fully stand-alone). I was curious if experienced eyes on the list could point out any serious flaws or suggestions. A multi-threaded signal concept inherently needs to be treated with some care, since the slots need to be prepared to be called from any thread -- or, preferably, signaling should be restricted by design to one thread. A particular weakness in this implementation is that the signal remains (recursively) mutex locked during the iteration through connected slot calls. I also have not added code for more than zero, one, or two parameter signals -- although it is trivial to do so. I hoped to get some feedback first (or find more bugs before I had to fix each one in 10 places). -braddock