destroy() not called in my servlet

I have a servlet whose init() method starts a thread (a "cleanup thread")
whose purpose is to watch over the threads created in doPost() and to stop
them after a timeout period.  I found that I was running out of memory after
running my servlet many times, and that this first thread (the "cleanup
thread") seems to be the culprit--if I don't start() it, I don't have the
memory leak.

The solution I would think would be to stop that thread in the servlet's
destroy() method. But I'm doing that; the destroy() method seems never to be
called.

Is there something I may be doing to prevent the destroy() method from
getting called??

Thanks.

Luke Call
EDM Group
Micron Technology, Boise