Thanks Paul, that did it. Here's the basics for anyone else that my need to know... pretty easy now in Flex III.
-Mark <mx:annotationElements> <mx:CartesianDataCanvas id="canvas" includeInRanges="true"/> </mx:annotationElements> public function cartChart():void{ canvas.clear(); canvas.lineStyle(1, 0xFF0000, 1, true, LineScaleMode.NORMAL); canvas.moveTo(hAxis.minimum, satisfactionMedian); canvas.lineTo(hAxis.maximum, satisfactionMedian); // canvas.moveTo(importanceMedian, vAxis.minimum); canvas.lineTo(importanceMedian, vAxis.maximum); }