Asperger's syndrome (AS) is a pervasive developmental disorder that may fall along the autistic spectrum. We compared the sleep of eight patients with AS with that of participants matched for age and gender. Patients with AS showed decreased sleep time in the first two-thirds of the night, increased number of shifts into REM sleep from a waking epoch, and all but one patient showed signs of REM sleep disruption. EEG sleep spindles were significantly decreased while K complexes and REM sleep rapid eye movements were normal. Three patients with AS, but none of the comparison participants, showed a pathological index of periodic leg movements in sleep. These observations show that sleep disorders are associated with AS and suggest that defective sleep control systems may be associated with the clinical picture of AS.