We studies all major characteristics of ldl incubated with blood serum. First change was decrease of sialic acid, and then we odserved the appearfnce of agtherogenicity. After that lipid decrease and size reduction take place. After thirty-six hour incubation increase of negative charge was observed. And finally, after forty-eight hours antioxidants decreased, susceptibility to oxidation increased and ldl particle became oxidized. You can see that oxidative modification is rather late event. The earliest change was desialilation of lipoprotein particle.