Please try the following: Test1 t1=new Test1(); | ArrayList<Test2> a=new ArrayList<Test2>(); | Test2 t2=new Test2(); | t2.setField(1);entityManager.persist(t2);a.add(t2); | t2=new Test2(); | t2.setField(2);entityManager.persist(t2);a.add(t2); | t1.setTest2s(a); | t1.setField(1); | entityManager.persist(t1); View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3956852#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...