Blood serum of 63 persons out of 191 men examined, randomly selected among non-organized population, caused in primary culture of mice peritoneal macrophages the 1.3-4-fold increased accumulation of intercellular cholesterol. Blood serum of other 128 men studied did not exhibit any atherogenic properties in the culture. The atherogenic potential of blood serum did not correlate with content of blood serum lipids, apolipoproteins B and A-I, while it correlated with the ratio apo B/apo A-I in blood serum and with one of ischemic heart disease risk factors--increased arterial pressure. Blood serum atherogenic potential, detected in experimental model, appears to be involved in development of human atherosclerosis.