Liver disease is associated with profound and characteristic changes in lipoprotein composition and metabolism. The most pronounced alterations are the formation of lipoprotein-X in intra- and extrahepatic cholestasis, the decrease of apolipoproteins A-I and A-II and the increase of apolipoprotein E. These alterations impair the activities of both lipoprotein lipase and lecithin: cholesterol acyltransferase. They are also responsible for an abnormal receptor mediated uptake of the lipoproteins from plasma. The abnormal lipid and apolipoprotein composition of the lipoproteins in liver disease appears to affect various important functions of cell membranes. The understanding of how these changes occur and their significance in the pathogenesis of other metabolic disturbances secondary to the abnormal lipid metabolism are important challenges for future research.