This study evaluated the effects of gender on response to a behavioral intervention that rewarded increases in PA with increases in access to TV viewing. 30 overweight or obese, 8- to 12-year-old children wore accelerometers every day for 8 weeks. Intervention kids accumulating 400 counts of PA on accelerometers earned 1 hour of TV time. Controls wore activity monitors but had free access to TV. Neither boys nor girls in the control group showed significant changes in overall PA or intensity of PA. Wearing an accelerometer in combination with rewarding PA with TV might be a more effective intervention for increasing overall PA and time spent in MVPA in overweight and obese boys than it is for overweight or obese girls.