I've found a related jax-ws topic: http://forums.java.net/jive/message.jspa?messageID=185244 Putting the Hashmap inside a wrapper does work: | @WebService() | @SOAPBinding(style = SOAPBinding.Style.RPC) | public class EchoMapSSTest { | | public static class MapWrapper { | public Map<String, String> map; | } | | @WebMethod | public MapWrapper echoMapSS(MapWrapper myMap) { | return myMap; | } | } | View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4041666#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...