Children with neuropsychiatric conditions, such as autism spectrum disorders (ASD), are at high risk for insomnia, and pharmacological treatments for insomnia in this population are acutely needed. Lack of restorative sleep may exacerbate disabling behaviors associated with ASD. Treatments that promote sleep in children with ASD may ameliorate these behaviors as well as strengthen the ability of parents to cope with this disorder and to assist their children in overcoming their disabilities. The long-term objectives are to determine if supplemental melatonin is an effective treatment for insomnia in children with ASD and whether the use of melatonin to treat insomnia improves these children's daytime behaviors and reduces levels of parental stress. This is a supplement to a previously awarded grant with the same title.