VITAL - VITamins to Slow ALzheimer's Disease (Homocysteine Study)

Inclusion Criteria: National Institute of Neurological Disorders and Stroke (NINDS)/Alzheimer's Disease and Related Disorders Association (ADRDA) criteria for probable Alzheimer's disease. Mini-Mental Status Examination (MMSE) score between 14 and 26, inclusive Stable medical condition for 3 months Stable medications for 4 weeks prior to the screening visit Physically acceptable for this study as confirmed by medical history, physical exam, neurologic exam and clinical laboratory tests Supervision available for administration of study medications Study partner to accompany subject to all scheduled visits Fluent in English or Spanish Modified Hachinski equal to or less than 4 CT or magnetic resonance imaging (MRI) since onset of memory impairment demonstrating absence of clinically significant focal lesion Able to complete baseline assessments 6 years of education or work history sufficient to exclude mental retardation Able to ingest oral medication Exclusion Criteria: B12 or folate deficiency Renal insufficiency (serum creatinine >=2.0) Active neoplastic disease (skin tumors other than melanoma are not exclusionary; patients with stable prostate cancer may be included at the discretion of the project director) Use of another investigational agent within 2 months History of clinically significant stroke Current evidence or history in the past 2 years of epilepsy, focal brain lesion, head injury with loss of consciousness and/or immediate confusion after the injury, or DSM-IV criteria for any major psychiatric disorder including psychosis, major depression, bipolar disorder, alcohol or substance abuse Blindness, deafness, language difficulties or any other disability which may prevent the subject from participating or cooperating in the protocol