you don't mention what version of arcmap or what level you have. In argis 10 there is a geoprocessing pulldown which has everything you need. the Union is what you will have to use. Then you can merge two polygons (in an edit session within the same layer) to end up with what you want. AlosAlso ET-geotools has free functionality to do this. And I believe Hawths tools has some free tools. I use ET tools. Ian-Ko Spatial Technologies