This protocol is a multicenter clinical trial of melatonin for sleep disturbances associated with Alzheimer's disease (AD). Frequent nocturnal awakening is a common behavioral symptom of AD. Nighttime wandering and agitated behavior may result in injuries and sleep disruption for caregivers. Alternatives are sorely needed to the currently available sleep medications that have marginal efficacy and serious side effects. Melatonin is a naturally occurring hormone secreted by the pineal gland. It has soporific effects with oral administration and is well tolerated. It enhances sleep in normal older people. Melatonin also may help sleep disturbances associated with AD; however, this remains to be proven.