I am working on the same project as Grant. The problem doesn't occur when we run a client to invoke the EJBs. Our project is layered into different applications. Hence we deploy multiple applications as multiple EARS in JBOSS. And yes, we have the exception classes packaged as JARs in the consumer EAR. When the isolation value in ear.deployer xml is set to false, the exception classes are loaded using same class loader. So, there is no problem.. I am able to catch the exception. But when I set the isolation atribute to true, the classes in the different EARS are loaded by different classloaders. Hence when the exception is thrown by the first EAR, the exception handling code in the second EAR is not recognizing it as the class that is loaded by the EAR's class loader. Interestingly, this happens just for exceptions, the user objects such as entities are passed properly from one EAR to another. probably, its a bug in JBOSS where it is not marshalling the class when it is supposed to do.. I believe this will keep you thinking..I will try to post some code tommorrow when i get into my office.. Thanks ila View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3974504#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...