Very important question arises: wat are factors of blood serum resposible for its atherogenicity. We have discovered that a certain fraction of low density liporotein is atherogenic, that is induces cholesterol accumulation in cultured cells. We demonstrated that lipoprotein of that fraction is multiple modified ldl. In addition, in blood of patients we have found autoantibodies to modified ldl. These antibodies interact with lipoprotein particle and increase its atherogenicity. Another way to increase atherogenicity of ldl is self-association of liporotein particles as well as association with other different particles, for example, conponents of extracellular matrix.