Hi ! Probably you want to access a relationship property when the entity bean is no longer under control of the entity manager (a "detached" entity). There are two ways around this problem: a) set the fetch type to "EAGER" @OneToMany(mappedBy="...", fetch=FetchType.EAGER) | public Collection<MyChild> getChilds() This causes the entity manager to load the child collection when the parent is loaded. May be a big performance problem. b) prefetch your childs when the entity bean is still under entity manager control. Imagine a find method of a session bean: public MyParent findById (Integer id) | { | MyParent parent = this.entityManager.find(MyParent.class, id); | parent.getChilds().size(); | } "parent.getChilds().size();" forces loading of the childen. Hope this helps Wolfgang View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4073303#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...