mySliderOnStage.getChildAt(1).width = 50;
mySliderOnStage.getChildAt(1).height = 100;
Thanks for posting your solution to this. I used it successfully with Flash Pro CS5.5. It's necessary for a slider that might be used with a touchscreen. Other links that I found stated that thumb width and height could not be changed and that it was necessary to extend the Slider component to access these properties.