Hi, I am trying to avoid thread locking problems when waiting using a boost::condition pseudo code: Main thread -- Start a worker thread -- boost::mutex::scoped_lock lock(m_Mutex); m_Condition.notify_one(); Worker thread boost::mutex::scoped_lock lock(m_Mutex); while (IsAlive()) { // do some work m_Condition.wait(lock); } As we can't predict which thread gets the mutex lock first lets assume that its the main thread. If this happens then m_Condition.wait will wait indefinitely as notify was called before wait. The only reliable way (that I can see) to prevent this is to never use wait, use a timed_wait instead and a loop. Why isn't the notification signal queued in the boost::condition object? Then the order of wait / notification would not be important. thanks Sam