Hi, It seems changing an immutable entity does not throw an exception. Instead the update statements just gets ignored. However additions/removals to an immutable collection throws a HibernateException. Is this correct? I also changed my test code to do something like this: public void testImmutableEntity() throws Exception { Session s = openSession(); Transaction tx = s.beginTransaction(); Country country = new Country(); country.setName("Germany"); s.persist(country); tx.commit(); s.close(); // try changing the entity s = openSession(); tx = s.beginTransaction(); Country germany = (Country) s.get(Country.class, country.getId()); assertNotNull(germany); germany.setName("France"); assertEquals("Local name can be changed", "France", germany.getName()); s.save(germany); tx.commit(); s.close(); // retrieving the country again - it should be unmodified s = openSession(); tx = s.beginTransaction(); germany = (Country) s.get(Country.class, country.getId()); assertNotNull(germany); assertEquals("Name should not have changed", "Germany", germany.getName()); s.close(); // // try deletion // s = openSession(); // tx = s.beginTransaction(); // s.delete(germany); // tx.commit(); // s.close(); // // s = openSession(); // tx = s.beginTransaction(); // germany = (Country) s.get(Country.class, country.getId()); // assertNotNull(germany); // assertEquals("Name should not have changed", "Germany", germany.getName()); // s.close(); } Changes to the entity seem to be properly ignored, but if I comment out the attempt to delete an entity the test fails. Personally I think it should be possible to delete the entity, however the documentation says: "may not be updated or deleted by the application". So my questions really are: 1. Is it correct that an immutable entity behaves differently than an immutable collection? For the former update statements just get ignored, for the latter a HibernateException is thrown. 2. Is the documetnation of immutable wrong - an immutable entity can be deleted? --Hardy