Thanks for the replies. 4l3xb, Yes, the request handler posts messages to the JMS queue and the onMessage method picks them up when they appear. Hitting the server with a benchmark tools gets the queue to grow to thousands of messages very quickly. The queue is then picked off very slowly by the message driven bean. There are two ways we've determined CPU usage. From sysstat, we've used: # mpstat -P ALL We've also used top, with the '1' command to list individual CPU usage. PeterJ, Sorry, forgot to mention. We're running a 32bit Linux 2.6 kernel from Kubuntu. We could try affinitizing the JVM to certain CPUs. Would you be able to advise how this can be accomplished? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4053405#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...