Therapy balls are air-filled rubber balls ranging from 20 to 30 in. in diameter that are sometimes used in place of traditional 4-legged chairs in classrooms. Unfortunately, research on the effects of therapy balls as chairs is limited. Therefore, this study evaluated the effects of therapy balls on the on-task behavior and academic performance of elementary students diagnosed with Attention Deficit Hyperactivity Disorder. An alternating treatments design was implemented with 4 students from the 3rd and 4th grades comparing therapy ball seating to traditional classroom chairs. No effect of the therapy balls was found, although students preferred sitting on the therapy balls. Teachers reported that the therapy balls were difficult to use and did not find them particularly effective.