Inclusion Criteria:

• 75 years or older.
• Fluent in English or Spanish.
• Stable medical condition for four weeks prior to screening visit.
• Stable medications for four weeks prior to screening visit.
• Either cognitively normal, or mild cognitive impairment. If MCI, the subject's CDR at screening have a global score of 0.5.
• mMMSE score greater than 88 for subjects with at least 8 years education, or greater than 80 for subjects with less than 8 years education, and FCSRT total free plus cued recall score greater than 44 with 3 learning trials.
• Willing to participate in four to five year follow-up study.
• Willing to identify person who can serve as informant.
• At least six years education or work history sufficient to exclude mental retardation

Exclusion Criteria:

• Meets DSM IV criteria for dementia
• History of clinically significant medical illness that would interfere with participation in trial, including active malignancy, myocardial infarction, or cerebrovascular accident within the past year
• Alcohol or substance abuse and/or active major psychiatric disorders
• Concurrent participation in a clinical drug trial
• History of mental retardation