Hi, I figured out that the problem was with the mappedBy in the non owning side of the ManyToMany relationship. What i still do not completely understand is what it maps to, is mappedBy = "students" mapping to the java.util.Set variable ? it can't map to the name because it is not students so does it map to the type of it, or possibly to the getter and setters (get/setStudents) ? If anyone can clear this up for me, i would be thankful. Andy View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3965639#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...