After doing some additional testing I've narrowed it down to a thread issue. It seems that once the load generates enough concurrent threads to hit the maxthread value the problem begins to appear. By upping the maxthread parameter for the 150 VU test (70 threads) I was able to get the problem to go away. I'm not trying to figure out how large to make the threads to get our 200 (currently testing 125 threads) and 250 VU tests to work. When we were testing this on BEA Weblogic Server 7.0 (SP5), we only needed 40 threads to handle our tests (150VU - 250 VU). I know that not all webservers behave the same, but so far I admit I'm a bit surprised by the amount of difference I'm seeing here with the thread behavior. While upping the thread count seems to "fix" the issue, this still sounds like some sort of defect to me. I would imagine that if all the threads are busy that they should be queing up until available threads become available. Each of our virtual users simulate end user activity and thus all of the users aren't busy all the time. There are definite peaks and valleys to the load. Anyways, as I continue the testing I'll post the results here as I have them. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3958055#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...