Hi there, seems the attention span for my last question is over. ;-) I also think that my subject was misleading. My question isn't about terminating, completing, or canceling a thread. It's about putting a thread in a blocked state. Please consider the following code. All functions, except for the run(), are called by the GUI thread. The _oThread object is RAII-object ( Resource Allocation is Initialization ). // Only called by GUI thread fvAsynchronousSequencer::fvAsynchronousSequencer() : _oThread ( ) , _bTerminateSequencerThread ( false ) , _bStop( false ) { _oThread.create( this, _run ); } // Only called by GUI thread fvAsynchronousSequencer::~fvAsynchronousSequencer() throw() { _bTerminateSequencerThread = true; // wake up the thread, if necessary _oRunCondition.notify_one(); // wait until the thread is terminated { boost::mutex::scoped_lock oLock( _oTerminateMutex ); _oTerminateCond.wait( oLock ); } } // Only called by GUI thread void fvAsynchronousSequencer::start() { _bStop = false; _oRunCondition.notify_one(); } // Only called by GUI thread void fvAsynchronousSequencer::stop() throw() { _bStop = true; // I would like to wait until the _oThread is a in blocked position. } void fvAsynchronousSequencer::_run() throw() { boost::mutex::scoped_lock oLock( _oRunMutex ); // Wait until someone calls start() _oRunCondition.wait( oLock ); do { // do something useful while( _bStop ) _oRunCondition.wait( oLock ); } while( !_bTerminateSequencerThread ); // now finish destructing the sequencer _oTerminateCond.notify_one(); } So, I will ask again my question. Is there a way that the stop() will only return when the worker thread in in blocked state? Right now, I just set _bStop to true and stop() returns. This approach is of course rife for deadlocks. Thanks again, Christian