Hi, assume that you have a relation "Person has many addresses" with two entities "Person" and "Address". If you declare a bidirectional relationship, your code can navigate from Person to Address, and from Adress to Person. With a unidirectional relationship, your code can navigate only from one side to the other. E.g. you can get the addresses of a person, but you cannot get the person of an address. The database representation of the relationship is not affected by your unidirectional/bidirectional decision. This defines only, how the code side looks like. Hope this helps Wolfgang View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4269767#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...