I've just started using the boost libraries, threads so far -- great libraries. I have a test app that uses thread groups of producers and consumers working with a queue. It seems simple enough, but I'm encountering a deadlock problem using notify_all() vs looping with notify_one() when ending the consumer threads. I'm not sure my implementation is correct though (link to source below). I can reliably cause deadlocks on all Windows XP systems I've tried (single, dual and quad machines) within about a minute of execution. However, I only had one deadlock on Windows 2000 (single or quad) in over 6 hours of execution and still going. Attaching or running the executable in the VS7 debugger shows all the threads and the main thread stopped in ntdll.dll via kernel32.dll. The stack shows the last user code executed by wmain was boost::thread_group::join_all from ctg.join_all(). The threads last ran boost::condition::do_wait before entering the kernel. Swapping lines 217-218 for 222-227 appears to fix the deadlock by looping with notify_one(). I would guess that something fundamental is wrong with my implementation, and my fix just changes the timing. Any help is appreciated. The source is posted at the link below. I can provide further information if necessary. Thanks, Joshua Boelter www.boelter.org/data/t_threadgroup.cpp Using Visual Studio 7.0.9466, stlport 4.5.3 (dll), boost libraries 1.29.0 on various WinXP Pro and Win2k systems.