According to EJB Spec, Session beans are non-reentrant i.e. one instance can only service one client at a time. This should be true for all EJB containers, including JBoss. Quoting the 2.0 spec: anonymous wrote : Non-reentrant instances | The container must ensure that only one thread can be executing an instance at any time. If a client | request arrives for an instance while the instance is executing another request, the container may throw | the java.rmi.RemoteException to the second request if the client is a remote client, or the | javax.ejb.EJBException if the client is a local client.[6] | Note that a session object is intended to support only a single client. Therefore, it would be an | application error if two clients attempted to invoke the same session object. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3972800#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...