You need to add a young generation size to the command line (usualy 1/3 to 1/4 the heap size): ... -XX:NewSize=300m -XX:MaxNewSize=300m Also, I am wondering about your client. If each request creates its own session, you could have a lot of session objects hanging around that will not be gc'ed until they time out. Also, I recommend charting the gcs (as mentioned in my presentation). This will tell you if there is a memory leak of some kind (such as sessions not timing out). View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4131912#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...