Partial ileal bypass is, today, the single most effective means available for lowering the plasma lipids, in particular the plasma cholesterol concentration. The cholesterol lowering effect of this procedure is universally lasting; response escape or rebound of lipid levels has not occurred. The operation is safe. In addition, the obligatory benefits of this mode of therapy make it attractive as a therapeutic alternative, especially in a young and asymptomatic population. We do not advocate this operation as the treatment of choice for all hyperlipidemic individuals. It may be the treatment of choice for certain patients with hyperlipidemia.