The relationship of weight at age 65 years and subsequent mortality was examined in a population of 1723 nonsmokers who were followed up from one to 23 years (mean, 9.5 years) during the Framingham Heart Study. In sex-specific proportional hazards analyses, risks of mortality were increased for men and women at the high and low extremes of body mass index, even when accounting for potential effects of excess weight on serum cholesterol level, blood glucose level, and systolic blood pressure. For those at the lower extreme of body mass index, the relative risk of death was almost twice as high in the years immediately after age 65 years as in later follow-up, suggesting that the increased early death rate was due to disease that was already present. At the upper extreme, risk of death was twofold over the entire follow-up period for persons with body mass indexes at or above the 70th percentile at both 55 and 65 years of age. We conclude that, even when accounting for cardiovascular risk factors, being overweight is a serious health problem for older people, especially for those with long-standing weight problems.