"petemuir" wrote : Yes, use a SMPC, not an extended PC. You don't want the @Transactional on those methods (it's an entity bean), and you probably want to let hibernate take care up updating the relationship for you - call entityManager.refresh(foo) to get hibernate to do this. I now tried to do the refreshing but had no luck. I stumpled acrross several Forum posts taht cite the following from the EJB 3.0 specs: anonymous wrote : | Note that it is the application that bears responsibility for maintaining the consistency of runtime | relationships?for example, for insuring that the ?one? and the ?many? sides of a bidirectional | relationship are consistent with one another when the application updates the | relationship at runtime. | Doesnt that mean i should do those gruppe.add/remove calls in Benutzer.setGruppe() ??? Greetings, Tobias View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4040912#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...