You'll need a ASM-3.x jar file - the profiler will switch to Javassist before GA. You can use the 1.0.CR4 release together wth AS-4.0: http://labs.jboss.com/jbossprofiler/ Please, note that its a completely different codebase and contains a binary module. See the documentation for further details. Otherwise just try the 2.0.CR8 together with AS-4.0 and report success/failure. Hope this helps ! View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4122898#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...