OBJECTIVE: The aim of the study was to investigate the specificity of sleep problems in children with autism and further explore the currently unclear association between sleep problems and daytime behaviour. METHODOLOGY: The Pervasive Developmental Disorder (PDD) group consisted of 31 children with autism and 7 children with Asperger's Disorder ranging in age from 44 to 152 months. The control group consisted of 36 children ranging in age from 63 to 171 months. The children were matched on age and gender, and group-matched on IQ level. A sleep diary was completed by parents over a 2-week period, in addition to several behaviour questionnaires. RESULTS: Results showed that children in the PDD group exhibited qualitatively and quantitatively different sleep patterns to nonautistic control children. CONCLUSIONS: The findings were discussed in light of current literature concerning circadian rhythm dysfunction, social difficulties, and abnormal melatonin levels in children with autism.