You are correct - JBoss 5 is not the same as JBoss 4. If you are just wanting to do Seam and have no specific reason to be on JBoss 5, I'd recommend staying on JBoss 4 so that you won't run into any differences. JBoss 5 uses Tomcat 6 and the JSF RI by default. It does not come with myfaces. It is very clear that your app is trying to use the myfaces StartupServletContextListener, which doesn't exist. I believe JBoss 5 comes with a version of the Seam booking application that you can use as a guide if you really feel the need to be on JBoss 5 now. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4010333#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...