High insulin levels and diabetes may increase the risk of Alzheimer's disease.We propose to conduct a double blind randomized placebo control trial of metformin, a medication that decreases insulin levels and prevents diabetes, in the prevention of memory decline among 20 persons with amnestic mild cognitive impairment, who are at increased risk of developing Alzheimer's disease. The duration of the trial will be 6 months. We expect to complete the trial in the 20 participants in 12 months. We are requesting two years of funding that include 2 months of study setup, 12 months of conduct of the trial, and 10 months for analysis of specimens, analysis of data, and preparation of related grants. This study targets two of the most important chronic conditions in elderly populations, hyperinsulinemia and cognitive impairment. The possibility that they are related is devastating. Thus, we must establish whether the reduction of hyperinsulinemia can prevent Alzheimer's dementia, and this study is a step in that direction.