Profiling would probably help in understanding what's happing there. When wsdl contracts with huge type models are involved, the port creation can be quite time consuming because a lot of classes are created. Perhaps you could evaluate re-using the port instance once it has been created. In case you're seeing different performance between the first invocation and following ones, instead, please refer to http://jbossws.jboss.org/mediawiki/index.php?title=Tuning. Finally, regarding the library comparison, I'd say also try using recent version of jbossws (from the libs names I'd say you're using old ones). View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4208416#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...