Circulating levels of cholesterol, specifically cholesterol associated with the low-density lipoprotein (LDL) fraction, have been established by observational epidemiologic studies and by metabolic, pathologic, genetic studies in humans and selected animal models, and by randomized clinical trials as a major etiologic factor in coronary heart disease. The ratio between the percent reduction in coronary heart disease incidence and the percent reduction in cholesterol levels associated with treatment in randomized trials, approximately 2:1, is almost exactly that predicted by numerous observational epidemiologic studies of this relationship. However, the clinical trials demonstrating that lowering LDL-cholesterol levels reduces subsequent incidence of coronary heart disease events have been confined by and large to middle-aged men with hypercholesterolemia as in the Lipid Research Clinics Coronary Primary Prevention Trial (LRC-CPPT) or to men with established coronary heart disease as in the Coronary Drug Project (CDP). Experimental confirmation that cholesterol-lowering treatment is worthwhile after as well as before age 60 is lacking. Thus, although the guidelines issued in October 1987 by the National Cholesterol Education Program's (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults did not discriminate explicitly by age, the absence of direct evidence of efficacy led them to allow room for physician judgment in applying their recommendations to older patients. This uncertainty in the application of the NCEP guidelines to older men and women is a matter of considerable consequence to the public health.