Physical activity is an important part of a healthy lifestyle for all people (Surgeon General’s Report, 1996) but is often overlooked in the lives of people with severe disabilities (Ellis, Cress & Spellman, 1994; Smith, 2000). For individuals with autism spectrum disorder (ASD), lack of communication skills and social functioning (APA, 2000), coupled with low motivation (Koegel, Koegel & McNerney, 2001; Reid, O’Connor, & Lloyd, 2003) and levels of skill and fitness (Reid & Collier, 2002) make participation in sustained physical activity difficult. Self-management is one technique that has been found effective in creating behavioural change in students with ASD (Koegel, Koegel & Carter, 1999; Koegel, Koegel & French, 2001) but there are few studies which have looked at the effect of self-management on participation in physical activity. Self-management is one aspect of self-determination which has increasingly been promoted as a critical factor for individuals with a disability (Reid, 2000; Wehmeyer, 2002). The purpose of this study was to determine the effect of self-monitoring, a subcomponent of self-management (Firman, Beare & Loyd, 2002) during a snowshoeing and walking/jogging program for individuals with ASD. Participants were three male secondary students attending a school for those with severe disabilities. Data were collected twice a week over a six month period. An AB time series design was used to determine the effectiveness of self-monitoring and recording distance covered during each snowshoe/walking session. The participants were asked to snowshoe or walk/jog around a circuit (207 m) at a local park. After baseline data were recorded, students were encouraged to participate through verbal prompting from aides, edible reinforcers after each quarter of the circuit, and self-recording by placing their own happy face on a board for each circuit completed. The edible reinforcers were systematically reduced over the course of the program from every 1/4 circuit to full circuit, the number of verbal prompts decreased, and the self montoring remained constant. Results were analyzed through graphic illustration and showed that all participants increased the distance snowshoed or walked/jogged over the course of the six months with simultaneous reduction of external reinforcement. Walking distances increased from 838 to 2072 meters, 1139 to 2277 meters, and 414 to 1242 meters for the three participants. This suggests that self-monitoring was an effective component of encouraging sustained physical activity participation for these students with ASD.