Hmm... why then do I get "detached object passed to persist" when I try to persist a newly created entity with collection mapping? I can persist anything just fine, but when I create an entity that holds a List of other entities (even when the list is still empty), that fails. I have already tried to merge() the entit instead of persisting it, but then em.find will return null for it while still in the same transaction. I would expect to see and use the entity later on to fill that collection... I am confused, Phil View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3978257#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...