Our review focuses on low density lipoprotein (LD lipoprotein) and very low density lipoprotein (VLD lipoprotein) in their roles as transporters of cholesterol and triglyceride and as factors contributing to premature arteriovascular disease. We describe the clinical manifestations of the common, primary hyperlipoproteinemias--that is, hyper-beta-lipoproteinemia, combined hyperlipoproteinemia, hyper-pre-beta-lipoproteinemia, and sporadic hyperlipoproteinemia--and discuss the variations in lipoprotein structure and metabolism that occur in these diseases. Based on an understanding of the physiologic control of lipoprotein metabolism, it is possible for the physician to alter the concentrations of LD lipoprotein and VLD lipoprotein by selecting a course of therapy appropriate to the specific disease. We describe the effects of obesity, diet, insulin, ethanol, estrogens, and the drugs clofibrate, nicotinic acid, and cholestyramine.