Epidemiologic studies suggest that the prognostic power of cholesterol levels diminishes with advancing age. Subdivision of the participants in several cohort studies into those above or below age 50 at entry shows that the increment in coronary heart disease risk per increment in total or LDL cholesterol level is nearly always substantially lower in the older group. In the Framingham Heart Study, the study with the most follow-up data beyond age 60, a 0.5 percent increment in the coronary heart disease incidence rate was estimated per 1 mg/dl increment in plasma cholesterol level -- about 60 percent of the increment seen in middle-aged men and women. However, the absolute numbers of potentially preventable coronary heart disease deaths, 80 percent of which occur after age 65, and myocardial infarctions attributable to high plasma cholesterol levels in Framingham and other observational studies appear to increase with increasing age.