We evaluated the effects of a modified version of the Good Behavior Game (GBG) on the number of steps taken by students during school recess. We divided a class into two teams, and awarded the team with the highest step counts at the end of each game raffle tickets for a school-wide lottery. The GBG was compared to recess periods without the game using an alternating-treatments design. Students took more steps while playing the GBG than they did during recess periods without the game.