I read the source of the interpretation of the <jar-file> tag and I found a tip which works with JBoss 4.2.1 : to put a relative path, put "../" only in the beginning of the path and next put "..\" as many as you need, so for me, it is : <jar-file>../..\entities.jar</jar-file> But I think that it will not work anymore with JBoss 5.0 but no problem with that, when it will be available, we will change the persistence.xml only for JBoss 5.0 and normally <jar-file>../../entities.jar</jar-file> will work with JBoss 5.0. Olv View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4095528#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...