Diabetes mellitus is a metabolic disorder, characterized by hyperglycemia and glycosuria resulting from a defect in insulin secretion, its action or both. Oxidative modification of LDL is recognized as one of the major process involved in the etiopathogenesis of diabetes mellitus. The aim of the present study is to investigate the LDL oxidation and its antioxi-dant potential in diabetes mellitus. The study was carried out in 80 diabetic subjects, classi-fied into two group according to their glycosylated hemoglobin (HbA1c) values as regulated (<0.50 M hexose/ M Hb) and unregulated (>0.60 M hexose/ M Hb). 40 healthy age matched subjects were also included for comparison. LDL from the serum sample was precipitated by heparin-citrate precipitation method. The LDL fractions were exposed to oxidation with CuSO4 and sensitivity to oxidation was evaluated. AOP was measured by taking 10 sub-jects from each group. The sensitivity of LDL oxidation was significantly higher in all dia-betic groups compared to control group. AOP was significantly decreased in unregulated diabetic group compared to control group. Low AOP probably shortens the lag phase of LDL oxidation so the sensitivity to oxidation appears to be higher in diabetes mellitus pa-tients.