In deciding whether to undertake a dietary program to reduce serum cholesterol levels, a person must consider how much benefit to expect. We developed a model that assumes cholesterol reduction is effective and safe in reducing the risk for death from ischemic heart disease. In the model, we considered asymptomatic adults with total serum cholesterol levels between 180 and 300 mg/dL. We defined risk status on the basis of blood pressure, smoking habit, and high-density-lipoprotein cholesterol level. For persons aged 20 to 60 years who are at low risk, we calculate a gain in life expectancy of 3 days to 3 months from a lifelong program of cholesterol reduction. For persons who are at high risk, the calculated gain ranges from 18 days to 12 months. Knowledge of the magnitude of the calculated benefits in increased life expectancy afforded by cholesterol reduction can assist persons in making decisions about dietary change.