The total fraction of low and very low density lipoproteins (LDL, VLDL), total cholesterol (TCS) and high density lipoprotein cholesterol (CS HDL) in arterial and venous blood was determined in 42 patients with atherosclerosis affecting predominantly arteries of the pelvis and the lower extremities. The mean concentration of the above-mentioned substances in the in-flowing and outflowing blood in the affected vascular region did not practically differ. At normal blood lipid level there exists a significant negative correlation between the absolute and relative CS HDL content on the one hand and, on the other hand, the arteriovenous difference in TCS content (r = -0.414 and -0.531 respectively). At hyperlipoproteinaemia, the CS HDL content correlates with the arteriovenous LDL and VLDL difference (r = -0.511). The findings attest to the fact that a decrease in the CS HDL level is accompanied by increased uptake of atherogenic substances in the peripheral vessels.