The version of ant that you are using does not have the ANTLR taskdef jar. You can download it from antlr.org. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4092797#4092797 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4092797