The hyperlipidemia of the nephrotic syndrome. Lipid abnormalities in patients with the nephrotic syndrome have long been recognized. However, the significance of these lipid abnormalities, the mechanisms producing them, and their potential treatment have all been a cause of debate. Recent data have helped clarify each of these areas of controversy. Studies of the lipoprotein abnormalities of patients with the uncomplicated nephrotic syndrome have shown that many will have elevated levels of total and low-density lipoprotein cholesterol, whereas only a few will have elevated levels of high-density lipoprotein cholesterol. If these lipid abnormalities have the same significance in this population as in other populations studied, then some patients with unremitting nephrotic syndrome will be at high risk for cardiovascular disease. The elevated cholesterol levels noted in the nephrotic syndrome are caused primarily by enhanced hepatic synthesis, with lesser contributions by decreased clearance and altered enzyme activities. The signal for enhanced hepatic lipogenesis may relate to changes in plasma albumin concentration, plasma oncotic pressure, a local effect of viscosity at the hepatic sinusoidal level, or a loss of urinary proteins or other liporegulatory substances. Recently, a number of short-term studies in nephrotic patients have documented the safety and efficacy of lipid-lowering drugs such as the bile acid-binding resins, probucol, and the HMGCoA (hydroxymethylglutaryl coenzyme A) reductase inhibitors. 