Sounds like your analysis on the RichFaces forum was on the right track. The session management layer does not prevent concurrent access to the session. The session's internal data structures can deal with concurrency (e.g. the attribute map is a ConcurrentHashMap) but if the objects you'll store in it are going to be accessed concurrently, they'll need to be thread safe or have access to them synchronized. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4155174#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...