Although several studies have examined the prevalence of comorbid psychiatric disorders in children with autism spectrum disorders, there are no current longitudinal studies of such children regarding the impact of comorbidity. In this study, 44 of an original sample of 175 preschoolers were located after 5 1/2 years, at an average chronological age of 10 years 3 months, and reassessed for comorbid disorders; a subsample was surveyed regarding use of special education and mental health services. Findings not only suggest continued comorbidity but also somewhat higher than expected use of behavioral services, often requiring out-of-school funding. The differential impact of comorbidity is discussed in relation to special education and access to related services. (Contains 3 tables and 2 figures.)