Studies involving physical exercise and individuals with autism spectrum disorders (ASD) were reviewed. Systematic search procedures identified 18 studies meeting predetermined inclusion criteria. These studies were evaluated in terms of: (a) participant characteristics, (b) type of exercise, (c) procedures used to increase exercise, (d) outcomes, and (e) research methodology. Across the corpus of studies, exercise was implemented with 64 participants with ASD aged 3-41 years. A variety of exercise activities were employed (e.g., jogging, weight training, bike riding). Following the exercise interventions decreases in stereotypy, aggression, off-task behavior and elopement were reported. Fatigue was not likely the cause of decreases in maladaptive behavior because on-task behavior, academic responding, and appropriate motor behavior (e.g., playing catch) increased following physical exercise. Results suggest that programs for individuals with ASD may benefit from including components designed to incorporate regular and specific types of physical activity. Areas in need of further research are discussed. (Contains 1 table.)