Changes in phospholipid composition of the erythrocyte membranes have been studied in experimental postmyocardial infarction cardiosclerosis. Erythrocyte membranes from animals with cardiosclerosis formed aftr experimantal occlusions of coronary arteries were characterized by significant decrease of a minor phospholipid, phosphatydylinositol (by more than 40%) and the increase of the major phospholipid, phosphatydylethanolamine. There was high content of lipid peroxidation products, malondialdehyde and conjugated dienes and the decrease in the activity of antioxidant enzymes, catalase and superoxide dismutase in blood serum of these animals.We have concluded the formation of postmyocardial infarction cardiosclerosis is accompanied by the increase of free radical reactions. This causes changes in phospholipid composition of cell membranes and the decrease of compensatory capacities of the enzymatic antioxidant system. These changes form a metabolic backgroung, which can influence cardiac remodelling properties.