Differences between 70 adults with autism spectrum disorders and intellectual disability and 70 age-matched adults with Down syndrome were examined on variables indicative of independence in adult life. Adults with autism spectrum disorder had less residential independence and social contact with friends, had more limited functional abilities and literacy, exhibited more behavior problems, had more unmet service needs, and received fewer services as compared to adults with Down syndrome. Reflecting these differences, adults with autism spectrum disorder were less likely to be classified as having high or moderate levels of independence in adult life as compared to adults with Down syndrome. Predictors of independence in adult life differed for adults with autism spectrum disorder as compared with adults who have Down syndrome. Implications for service delivery are discussed.