The prevalence of sleep disturbances in 52 children with Asperger syndrome (AS) as compared with 61 healthy controls (all subjects aged 5-17 years) was investigated. Problems with sleep onset and maintenance, sleep-related fears, negative attitudes toward sleeping, and daytime somnolence were more frequent among children with AS than among controls. Short sleep duration (less than 9 hours) was almost twofold (59% vs. 32%), and the risk for sleep onset problems more than fivefold (53% vs. 10%) more common in the AS group than in the control group. Child-reported sleeping problems were also more prevalent in the AS group than in controls (58% vs. 7%). The results suggest that sleep disturbances should be routinely evaluated in children with AS.