We have discovered that low density lipiprotein circulating in the blood of patients and responsible for atherogenicity of blood serum is multiple modified particle. I would like to specially emphasize that this modification is not only oxidative modification. There are numerous physico-chemical characteristics which are altered in lipid, protein, and glycoconjugate moiety of lipoprotein particle. As compared to native ldl multiple modofied particle has lower level of neutral carbohydrates and lipids, higher level of some phospholipids, smaller sise, higher density, higher negative charge, increased susceptibility to oxidation and aggregation. The most important property of multiple modified ldl is the ability to accumulate lipids in arterial cells that is atherogenicity.