Aim To investigate the effect of telmisartan on vascular endothelial function in patients with metabolic syndrome.Methods 76 cases of patients with metabolic syndrome were recruited,and randomized to receive conventional treatment(n=38) or telmisartan(80 mg/d) on the basis of conventional treatment(n=38) for 3 months.Thirty-eight healthy persons were chosen as control group.The plasma level of glucose and lipid metabolism,nitric oxide(NO) and cytokines of each group before and after treament were determined.The blood pressure and endothelial relaxation function were also measured.Results The blood glucose and blood pressure in telmisartan group and conventional group were all decreased after treatment(P<0.01),without intergroup differences(P>0.05).In telmisartan group,the flow-mediated diameter(FMD) and NO were obviously increased(P<0.05 and P<0.01),and the plasma tumor necrosis factor α(TNF-α),interleukin-6(IL-6) and C-reactive protein(CRP) were decreased(P<0.05),with intergroup differences(P<0.05).No obvious changes of FMD,NO and inflammatory factors were found in conventional group.Conclusion Telmisartan can improve vascular endothelial function in patients with metabolic syndrome by raising concentration of NO and inhibiting inflammatory reaction with decreased level of cytokines.