I want a singleton MDB so that only one message gets processed at a time. I.E. receive the message from the queue, process the message in its entirety, then process the next message. I have deployed the jms service as deploy-hasingleton, and I have the @ActivationConfigProperty for maxSession set to 1. Here is what looks like is happening. 1. Receive message from queue (mark as complete or acknowledge) 2. Receive another message from queue before 1st message is done processing. I have also tried to set the @ActivationConfigProperty for acknowledgeMode to Client-acknowledge, but I am not sure that works since jboss does not document that. This was so that I could call message.acknowldge() when I am done processing so that the next message would not start processing. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4237739#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...