The @ManyToMany definition on one of the sides is incorrect. For bidirectional relationships one side must be the owner. The side using "mappedBy" is the inverse side, which means it updating it does NOT update the relationship. If this was generated it's probably a seam gen bug. To fix your generate objects you'll need to do the following to ONE of the @ManyToMany's. 1) Remove the mappedBy attribute 2) Add a @JoinTable So updating A to be the owner side does this. B would be unchanged. If you want B to be the owner side do the same but swap A_ID and B_ID round in the joinColumns/inverseJoinColumns attributes. | @ManyToMany(cascade = CascadeType.ALL, fetch = FetchType.LAZY) | @JoinTable( | name="C", | joinColumns={@JoinColumn(name="A_ID")}, | inverseJoinColumns={@JoinColumn(name="B_ID")} | ) | Submit a bug report JIRA and I'm sure something will fix it, although guessing the owner side will be fun. HTH. Mike. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4031431#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...