Melatonin is an endogenous indolamine produced by the pineal gland which may have a role in the biological regulation of circadian rhythms, sleep, and mood. Melatonin receptor activation in the hypothalamus likely regulates circadian rhythms. In the United States, melatonin is marketed as a dietary supplement. Clinical trials in children and adults have shown modest clinical benefit in the treatment of insomnia. Adverse events reported in patients receiving melatonin were not significantly different in type or occurrence from those reported in patients receiving placebo. Considering the potential for benefit, lack of significant adverse events, and lack of abuse potential, melatonin may be considered a valid therapeutic option for improving outcomes in certain pediatric and adult patients with insomnia.