The principal goal of dietary treatment of heterozygous familial hypercholesterolemia (hFH) is the reduction of the plasma low density lipoprotein (LDL) cholesterol. This is best accomplished by enhancing the activity of LDL receptors and, at the same time, depressing liver synthesis of cholesterol. Both cholesterol and saturated fat down-regulate the LDL receptor and inhibit the removal of LDL from the plasma by the liver. Saturated fat down-regulates the LDL receptor, especially when cholesterol is concurrently present in the diet. The total amount of dietary fat is also important. The greater the flux of chylomicron remnants into the liver, the greater is the influx of cholesterol ester. In addition, factors that affect LDL synthesis could be important. These include excessive calories (obesity) that enhance very low density lipoprotein (VLDL) and, hence, LDL synthesis, and weight loss and omega-3 fatty acids, which depress synthesis of VLDL and LDL. The optimal diet for treatment of children and adults has the following characteristics: cholesterol (100 mg/day), total fat (20% of kcal, 6% saturated with the balance from omega-3 and omega-6 polyunsaturated and monounsaturated fat), carbohydrate (65% kcal, 67% from starch), and protein (15% kcal). This low-fat, high-carbohydrate diet can lower the plasma cholesterol 18-21%. A new concept, the Cholesterol-Saturated Fat Index, allows people to evaluate any foodstuff for its potential to elevate the plasma LDL cholesterol level. It is an antithrombotic diet, thrombosis being another major consideration in preventing coronary heart disease. Also, it contains significant amounts of antioxidants and fiber. Dietary therapy is the mainstay of treatment of hFH to which various drug therapies can be added.