Inclusion Criteria:

• Prior to participation in this study, each prospective study individual must sign an informed consent form.
• Diagnosis of probable or possible Alzheimer's disease according to NINDS-ADRDA and DSM-IV criteria.
• Not actively participating in another clinical drug trial.
• MMSE range 12-28 at entry.
• Hachinski Modified Ischemic score < or =4.
• Accompanied by appropriate caregiver who can aid in administration of medication and make assessments.
• Good general health as evidenced by physical, neurological and clinical laboratory examination.
• Education level > or = 9th grade or equivalent.
• Fluent in the English language.
• Reliable caregiver.
• Able to complete neuropsychological tests.
• Ambulatory.
• On stable doses of medications for the treatment of non-excluded medical conditions for four weeks prior to screening.
• Able to participate in all scheduled evaluations.
• Geriatric Depression Scale < or = 20.
• Not exceeding 400 IU of Vitamin E for 30 days.
• For patients currently taking donepezil, they must remain on a stable dose for at least three months. Individuals taking stable doses of other cholinesterase inhibitors can be included, but no study subject may initiate use of any cholinesterase inhibitor after entrance to trial.
• Individuals of both sexes over 50 years of age will be eligible.

Exclusion criteria:

• Significant neurological or psychiatric disease other than Alzheimer's disease.
• Patients with known or suspected Parkinsons's disease or dementia with Lewy bodies.
• Significant systemic illness (including uncontrolled hypertension) or organ failure.
• History of mental illness within one year or history of significant untreated cardiac or thromboembolic vascular disease (arrythmias, unstable angina, CVA, deep venous thrombosis, or pulmonary embolus).
• Current chronic use of anti-cholinergic medications (anti-histamines, and Artane or Cogentin). Stable doses of anxiolytics, sedatives, hypnotics, antipsychotics and SSRI antidepressants are acceptable. The use of any antipsychotics or tricyclic anti-depressants must be reviewed prior to entry.
• Diagnosis of major depression according to DSM-IV criteria in the last two years.
• Allergies to atorvastatin or HMG CoA reductase inhibitors.
• Pregnant women.
• History of head injury.
• On a cholesterol lowering drug at time of enrollment.
• History of significant liver disease and or elevated transaminases.
• Cholesterol level lower than 90 mg% at initial screening