Children with autism spectrum disorders (ASD) often exhibit sleep and behavioral disorders. Treatment of sleep disorders can be difficult in these children. Clonidine, an alpha2-adrenergic receptor agonist, has been shown to be effective in reducing impulsivity, inattention, and hyperactivity, as well as in serving as a sedative for medial procedures. An open labeled retrospective study of clonidine in treatment of insomnia, and/or hyperactivity, inattention, mood disorder, and aggressive behaviors was conducted using parent reports of sleep initiation and maintenance, as well as behaviors prior and during clonidine treatment. Clonidine was effective in reducing sleep initiation latency and night awakening, to a less degree in improving attention deficits hyperactivity, mood instability and aggressiveness in this cohort of 19 children with ASD. The side effects were largely tolerable. Further evaluation with placebo-controlled double-blind clinical trial of clonidine use in ASD will provide more insight into the clinical efficacy and safety of the medicine in ASD.