Sorry for the spam on the updates :) - but, its the same thread printing this out too. I changed the print line to: curThread = threading.current_thread() print("Started subproc: PID: %d : args: %s Thread ID: %s" %(newJob.pid, str(args), str(curThread.ident))) and got the output: Reaping PID: 23707 True Started subproc: PID: 23709 : args: data1 Thread ID: 12 Started subproc: PID: 23709 : args: data1 Thread ID: 12 poll isalive: True Started subproc: PID: 23710 : args: data2 Thread ID: 13 poll isalive: True Again, I can't see how this could pring it out twice? Could this be related to the problem we are having? Altgough I do seem to get the line twice on 2.6.3 as well - but nothing like as often..