Use XMLListCollection as the PopUpMenuButton data source
<?xml version="1.0"?> <mx:Application xmlns:mx="http://www.adobe.com/2006/mxml" layout="absolute"> <mx:PopUpMenuButton labelField="@label"> <mx:dataProvider> <mx:XMLListCollection> <mx:XMLList> <item label="ActionScript"> <item label="S" /> <item label="B" /> </item> <item label="MXML"> <item label="A" /> <item label="C" /> </item> </mx:XMLList> </mx:XMLListCollection> </mx:dataProvider> </mx:PopUpMenuButton> </mx:Application>