Individuals with autism often lack motivation to engage in sustained physical activity. Three adolescents with severe autism participated in a 16-week program and each regularly completed 30 min of cycling at the end of program. This study investigated the effect of a self-regulation instructional strategy on sustained cycling, which included self-monitoring, goal setting, and self-reinforcement. Of particular interest was the development of self efficacy during the physical activity as a mediator of goal setting. A multiple baseline changing criterion design established the effectiveness of the intervention. The results suggest that self-regulation interventions can promote sustained participation in physical activity for adolescents with severe autism. (Contains 1 table and 4 figures.)