The present study sought to describe the profile of sleep disturbance reported in children with autistic spectrum disorders (ASDs) and to document any sleep disorders underlying reports of sleeplessness. Sixty-nine children aged 5 to 16 years (mean 9 years 4 months, SD 2 years 7 months; 14 females) with an ASD were assessed by detailed sleep histories taken from parents, the Simonds and Parraga Sleep Questionnaire, a 2-week sleep diary, and actigraphs worn by the child for five nights. Parent-reported sleeplessness featured prominently (64%). Sleep disorders underlying the sleeplessness were most commonly behavioural (i.e. to do with inappropriate sleep-related behaviours), although sleep-wake cycle disorders and anxiety-related problems were also seen. In addition, the sleeplessness patterns of a large minority of children could not be classified by conventional diagnostic criteria. Sleep patterns measured objectively did not differ between those children with or without reported sleeplessness, but the sleep quality of all children seemed to be compromised compared with normal values.