This study examined sleep patterns, sleep problems, and their correlates in children with autism spectrum disorders (ASD). Subjects consisted of 167 ASD children, including 108 with autistic disorder, 27 with Asperger’s syndrome, and 32 with other diagnoses of ASD. Mean age was 8.8 years (SD = 4.2), 86% were boys. Parents completed a self-administered child sleep questionnaire. Results showed that average night sleep duration was 8.9 h (SD = 1.8), 16% of children shared a bed with parent. About 86% of children had at least one sleep problem almost every day, including 54% with bedtime resistance, 56% with insomnia, 53% with parasomnias, 25% with sleep disordered breathing, 45% with morning rise problems, and 31% with daytime sleepiness. Multivariate logistic regression analyses indicated that younger age, hypersensitivity, co-sleeping, epilepsy, attention-deficit/hyperactivity disorder (ADHD), asthma, bedtime ritual, medication use, and family history of sleep problems were related to sleep problems. Comorbid epilepsy, insomnia, and parasomnias were associated with increased risk for daytime sleepiness. Results suggest that both dyssomnias and parasomnias are very prevalent in children with ASD. Although multiple child and family factors are associated with sleep problems, other comorbid disorders of autism may play a major role.