The principal goal of dietary treatment of familial hypercholesterolemia (FH) is the reduction of the plasma low density lipoprotein (LDL) cholesterol. This is best accomplished by enhancing the number 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 kcalories, 6% saturated with the balance from omega-3 and omega-6 polyunsaturated and monounsaturated fat), carbohydrate (65% kcalories, two thirds from starch), and protein (15% kcalories). This low-fat high-carbohydrate diet can lower the plasma cholesterol 18% to 21%. It is also an antithrombotic diet, thrombosis being another major consideration in preventing coronary heart disease. Dietary therapy is the mainstay of treatment of FH to which various drug therapies can be added.