If we want duplicate detection to work between failures of the jms client then we need to do it on the server side. It also needs to work between failures of the server so needs to be persisted in persistent storage. This is certainly going to be a performance drag so I suggest we add a feature request for it, and it to be off by default. We should probably implement it by keeping a cache of message or transaction id. The entries time out and are evicted after a certain amount of time which can be specified by the client. As genman has pointed out, this is not a common feature in messaging systems so I am not too worried if we don't implement this immediately. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3977154#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...