Hello, All I've hit a minor snag in my understanding of ManyToMany relationships with EJB3. In a nutshell, I have a Post Entity which as a ManyToMany relationship with a Keyword Entity. I'm decided to create my own junction table. The Keyword table has a unique key constraint on the keyword field. The Issue: I can persist new Post entities with non-existing Keywords entities (e.g. Keywords that don't exist in the database ) But , When I attempt to attach an existing Keyword entity to a non-persisted Post object the persist fails for the following reason. org.hibernate.PersistentObjectException: detached entity passed to persist: com.example.web.jList.ejb.entity.Keyword My understanding: What i'm expecting is that if i attach an existing Keyword entity to the Post entity then i should have a new row in my Post/Keyword junction table. I main question is what am i doing wrong? JBoss 4.0.5GA JEMS install with EJB3 support My database looks like so: Post Table idtitledescriptionpostdatelogin_idprohibitedevents_id 1Moving Sale Everything must GO!!!!Test2006-11-16 19:22:02101 2Once's in a life time Sale!!!!Test 22006-11-16 19:22:02102 Post/Keyword Junction Table idposts_idkeywords_id 113 224 311 416 515 621 Keyword Table idcountversionkeyword 100car 200tools 300toys 400computers 500babys toys 600car parts | // In my Post Entity | @ManyToMany( fetch = FetchType.EAGER , cascade = CascadeType.ALL) | @JoinTable( name="keyword_posts_junc", | joinColumns={@JoinColumn(name="posts_id")}, | inverseJoinColumns={@JoinColumn(name="keywords_id")} ) | public Set<Keyword> getKeywords() { | return keywords; | } | View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3990853#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...