The costs and benefits of cholesterol lowering in the primary prevention of coronary artery disease (CAD) were considered using lifetime lovastatin therapy as the intervention model for adults between 35 and 55 years of age. The analysis projected the benefits of CAD risk reduction using estimates from the Framingham Heart Study. The chosen analytic perspective was that of the patient. For average-risk men with total serum cholesterol levels between 5.69 and 9.83 mmol/liter (220 and 380 mg/dl), the cost per life-year saved ranged from $9,000 to $106,000, whereas for average-risk women, the cost ranged from $35,000 to $297,000 (1989 U.S. dollars). In high-risk men (with smoking habit and hypertension), the cost per life-year saved values ranged from 6,000 to $53,000, whereas in high-risk women the cost per life-year saved values ranged from $19,000 to $160,000. The results were more favorable than those found in previous studies of alternate medication therapies for hypercholesterolemia. Even using conservative parameter assumptions, at least 800,000 Americans aged 35 to 55 years are at sufficiently high risk for CAD, so that the net cost of lovastatin therapy can be favorably compared with other widely used medical interventions.