#DEFINE THREAD_PRIORITY_LOWEST -2 #DEFINE THREAD_PRIORITY_BELOW_NORMAL -1 #DEFINE THREAD_PRIORITY_NORMAL 0 #DEFINE THREAD_PRIORITY_ABOVE_NORMAL 1 #DEFINE THREAD_PRIORITY_HIGHEST 2 DECLARE SHORT SetThreadPriority IN Win32API; INTEGER hThread, INTEGER nPriorityThe function will return non-zero if it succeeds. I don't know if the _VFP.ThreadID can be used here or not. Further, under NT you must have certain rights to call this. Not being an NT user I really can't help about that.