It seems the wsdl file has an empty type for HashMap, see this: <xs:complexType abstract="true" name="abstractMap"> | <xs:sequence/> | </xs:complexType> | The abstractMap type contains nothing (an empty sequence). So there seems to be a problem with mapping the original type on the server side. What version on JBossWS are you using? The one that comes bundled on JBoss AS 4.2.x? View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4147569#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...