Aim To study relationships between the carotid intima-media thickness(IMT)and serum malondialdehyde(MDA),superoxide dismutase(SOD)activity in the patients of impaired glucose regulation(IGR)and the effects of probucol on MDA,SOD and carotid IMT.Methods 50 subjects with Type 2 diabietes mellitus(T2DM),24 with IGR and 28 with normal glucose tolerance(NGT)were recruited in the study.Carotid IMT were assessed by the high-resolution B-mode ultrasound unit.Serum SOD was measured by xanthine oxidase method and the serum MDA by thiobarbituric acid method.Plasma endothelin-1(ET-1)was detected by radioimmunoassay.All the patients with T2DM or IGR were randomly divided into treatment group and control group.The treatment group received probucol(0.5 g,twice a day)on the base of previous treatment,while the control group only kept their routine treatment.The examinations were repeated in 12 weeks after treatments.Results Carotid IMT of T2DM group and IGR group were significantly higher than that of NGT group(P<0.01).Compared with that in subjects of NGT,the MDA and ET-1 level were increased in patients of T2DM or IGR(P<0.01),and ET-1 was also significantly different between the T2DM and IGR groups(P<0.01).While serum SOD activity showed a significant difference among the three groups.It was found that T2DM group was the lowest,IGR group followed by,and NGT group the highest(P<0.01).Paper showed that carotid IMT kept positive with MDA,ET-1,FBG,PBG,duration,HbA1c and LDLC(P<0.05),while negative with SOD in all the groups.In multiple linear stepwise regression,MDA,ET-1 and LDLC showed a significant association with carotid IMT.After intervention with probucol,MDA and ET-1 decreased,while SOD activities increased.Conclusions The study suggests that there have been disorders of endothelial function and oxidative system during the prediabetic state.Probucol may inhibit oxidative stress,improve endothelial function and provide a new idea for the prevention of early atherosclerosis in IGR.