Diet is the common denominator in the treatment of hyperlipidemia. Calorie and alcohol restriction are often prescribed for hypertriglyceridemic subjects. When these subjects lose weight their serum triglycerides often decrease, secondary to a diminution in hepatic triglyceride secretion. There is also a reduction in insulin resistance leading to an improvement in carbohydrate tolerance. Because some hypertriglyceridemic subjects over-synthesize triglycerides after alcohol ingestion, alcohol restriction is important in the dietary therapy of these patients. Although controversial, the restriction of cholesterol and saturated fat intake is often prescribed for hypercholesterolemic subjects. Recent evidence show (a) As the daily absolute cholesterol intake increases, the % absorbed is decreased but the amount absorbed per kg body weight is increased. (b) Hypercholesterolemic subjects differ from normal subjects in their response to cholesterol and fat intake. (c) A high cholesterol and high saturated fat diet increases the cholesterol concentration in all lipoprotein fractions. A low cholesterol and high polyunsaturated fat diet has the opposite effect. (d) These diets also affect serum apoprotein levels (apo B and apo A-I). It is becoming evident that hyperlipidemic subjects respond differently from normal subjects to dietary changes. For these subjects, at greater risk of developing atherosclerosis, dietary therapy is important.