Serum concentrations of total cholesterol, HDL cholesterol, triglycerides and apolipoproteins A-I and B were studied in black subjects with no known risk factor for coronary heart disease and in subjects with a single risk factor. The concentrations of lipids and apolipoproteins were sex-dependent. HDL cholesterol and apolipoprotein A-I were age-dependent in females (P less than 0.05 and P less than 0.01, respectively). There was a dose-related association between alcohol consumption and serum concentrations of triglycerides, HDL cholesterol, apolipoproteins A-I and B in males (P less than 0.001 and P less than 0.002, respectively in the heavy drinkers). The effects of cigarette smoking on the concentrations of serum lipids and apolipoproteins appear to be prominent in the heavy smoking subjects (P less than 0.001 and P less than 0.001, respectively). This work suggests that HDL cholesterol and apolipoprotein A-I may discriminate black subjects at risk of developing atherosclerosis.