The serum autoantibody against malondialehyde modified low density lipoprotein(MDALDL)was investigated in the healthy and hyperlipidemic patients of different age groups,Our results showed:①The autoantibody concentration of MDALDL in the healthy increased with aging , and showed the remarkable increase in male over 4 5 years and female over 65 years.The autoantibody concentration of male was markedly higher than that of female in the group 45 years~ 64 years; No difference between male and female was found in other age groups.②The autoantibody concentration of MDA-LDL in the hypertriglyceromic and mixedly haperlipidemic group was higher than that of the healthy group in all age groups.The autoantibody concentration of the hypercholesterolemia was much higher than that of the healthy in groups before 45 years,But in the groups over 45 years, no significant difference was seen between the hypercholesterolemic and the healthy. It was suggested that the serum concentration of autoantibody against MDA-LDL was affected by age and sex,and related to the level of the serum lipids.