Hi ! I think you have to use a generic list so that the container can determine which type is contained in the list: public class Team (...) | @OneToMany(mappedBy="team") | private List<User> teamList; The snippet of class "User" seems to be wrong, you probably meant this: public class User (...) | | @ManyToOne | @JoinColumn(name="team_id",referencedColumnName="id") | protected Team team; Hope this helps Wolfgang View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4002245#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...