Single administration of hydrocortisone into rabbits with experimental atherosclerosis increased the content of atherogenous classes of lipoproteins (Low Density Lipoproteins (LDL) and Very Low Density Lipoproteins (VLDL) in the animals with distinct atheromatosis. Content of the lipoproteins was decreased in animals, which had no atheromatous alterations in aorta under the effect of atherogenous diet. Within 5 hrs after the single administration of hydrocortisone in rabbits with pronounced atheromatosis of aorta relative content of cholesterol was increased in the VLDL fraction. In rabbits, resistant to development of atheromatosis, composition of VLDL was not altered. Under the effect of hydrocortisone the LDL fraction fo lipid composition was altered in the direction of relative increase in triglycerides content. In the LDL fractions subfractions were observed, which were similar to the VLDL in their cholesterol/triglycerides ratios. The data obtained suggest that in blood plasma transformation of the lipoproteins was impaired under the effect of hydrocortisone. Hydrocortisone influenced the spectrum and lipid composition of lipoproteins in blood serum independently of the degree of hypercholesterolaemia.