Sleep disorders in children with autism can produce devastating stress on their families, and have been associated with the children's increased daytime hyperactivity and diminished attention. Parents of children with autism report encouraging results in helping their children fall asleep at night after giving them the dietary supplement melatonin. A naturally occurring neurotransmitter, melatonin has been shown to affect sleep/wake cycles when levels are low. While side effects of from using the melatonin dietary supplement appear to be few, no controlled clinical studies have been conducted to test its efficacy and determine optimum doses and time of administration. Doses used range from 1 to 10 mg, and the time that parents give it to their children range from hours to 30 minutes prior to bedtime. The researchers eventually plan to apply to other sources for funding for a large-scale randomized clinical trial to determine melatonin's efficacy, and in preparation for that they will conduct a pilot study to determine safety, optimum dose and time of administration. They will enroll 20 children with autism whose parents report on standardized tests that sleep disorders are a major problem. Prior to and after the clinical study of melatonin, parents will record their child's sleep patterns through "sleep diaries", their child's behavior, and parental stress levels. Then, parents will begin giving their child liquid flavored melatonin in gradually increased doses, from 1 mg. to a maximum tolerable level under 10 mg. Parents also will change, mi-way through the study, the time of giving melatonin from 30 minutes to five hours prior to their child's bedtime. Children will wear activity meters (watch-like devices) on their wrists that quantify movement and rest as a surrogate for wakefulness and sleep. Through the pilot study, the researchers will determine optimal dose, timing, and safety and tolerability of melatonin, and determine any needed modifications in the behavioral and stress scales to be used in the anticipated randomized clinical trial. Significance: This pilot clinical trial should establish the guidelines for undertaking a randomized clinical trial to determine whether dietary supplement melatonin effectively promotes sleep in children with autism-related insomnia, and reduces related parental stress. The results of the large-scale study, in turn, should improve medical management of autism-related insomnia.