Abort is not releasing memory

HI I have a program that connects to server and forwards data to another server. When I want to kill the app i dequeue the threads that I have created and call abort on them. while (MyList.Count > 0) { try { ((Mythread)MyList.Dequeue()).Abort(); } catch { } } The app (gui) disappears, but the threads remain in memory. Any ideas why the threads aren't dying and releasing memory? thanks