It is proposed that hyperlipoproteinemias could be characterized according to their apolipoprotein concentration and composition. Apolipoprotein profiles will be studied in experimentally induced hyperlipoproteienemic rats and monkeys, to demonstrate the difference in apolipoprotein patterns between control and hyperlipoproteinemic animals. The changes in apolipoprotein profiles between hyperlipoproteinemias of different origin will be compared, and the effect of hypolipidemic drugs will be studied. The synthesis and the rate of removal of biologically labeled apolipoproteins will be studied, using a method which permits the determination of the apolipoprotein radioactivity in its physiological state (without isolation of the lipoproteins). The development of hyperlipoproteinemia and corresponding changes of apolipoprotein profiles will be correlated with the development of atherosclerosis. The presence of apolipoproteins in the atherosclerotic tissue will be determined and its concentration and flux will be correlated with the serum apolipoproteins.