I think there should be MaxPoolSize rather than a maxSession property. When I set my MDB to have a maxSession of 1 (to get a singleton), and send multiple messages to the Queue, indeed only one MDB is actually being processed (as confirmed in my logs). However, when I go to the JMX-console and click on the queue to which my MDB is listening, I can see that the property InProcessMessageCount has a value of 2. This would suggest at least 2 MDB's are attempting to process messages rather than a singleton. Why is this? Could this be a bug? What im trying to do is wipe out all messages from the Queue including the one's that are in process. I am able to do this by getting access to the MBean for messages that are "waiting" in the queue and invoking the "removeAllMessages" method. However, I am unable to delete the messages that are "in process", except the one that is actively running. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3996947#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...