I have the same problem using 2 jars in an ear file. But neither the class nor the jar-file tag in a persistence.xml of the META-INF directory of the ear file works. The aim is to have a basic.jar where general entity classes exist. In the concrete.jar I would like to have derived entity classes from the basic.jar. Both should use the same persistence unit. I use JBoss 4.2.0 GA. It would be nice if benc could send his readjusted ejb3jar project to me. Thanks, Thomas View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4081706#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...