Not all ldl particles circulating in the blood of patients have low level of sialic acid and ather alterations specific for modified atherogenic liporoteins. Even in nonatherogenic plasma of healthy donors we have found modified ldl. However the portion of modified lfl in the blood of healthy individuals doed not exceed ten percent while in patients mean value of modified ldl is thirty-five percent. So, the existance of atherogenicity in blood is not a question of quality of all ldl particles, but a questuion of modified ldl proportion. The proportion of modified ldl in atherogenic blood varies from fifteen to eighty percent.