Modafinil, trade named Provigil, is a medication approved by the Food and Drug Administration for the treatment of narcolepsy, obstructive sleep apnea/hypopnea syndrome, and shift work sleep disorder. Each of these problems is characterized by difficulty sleeping at night and excessive daytime sleepiness. Modafinil is prescribed during the day to counteract this sleepiness. The idea behind this treatment is that sleepiness that leads to napping during the day prevents a patient from being tired or sleepy enough to get good sleep at night. This study is designed to determine if the medication can "reset" participants' sleep/wake rhythm to a more normal rhythm.

Inclusion Criteria:

• A clinical diagnosis of Alzheimer's disease or Mild Cognitive Impairment
• Subjective complaint of sleep disruption, unsatisfactory sleep, early morning awakening, early bedtime, or excessive daytime sleepiness. Such complaint can be made by either the potential participant or by the caregiver.

Exclusion Criteria:

• Participation in any other clinical drug trial
• Liver failure
• Believed by the investigator to be unwilling or unable to follow the protocol
• Active liver or coronary disease

Early termination leading to small numbers of subjects analyzed