Abstract: AIM: To investigate the effects of angiotensin II receptor antagonist telmisartan on the vascular reactivity and expression of uncoupling protein 2 in rats with metabolic syndrome (MS). METHODS: Male wistar rats, aged 2-month-old, were divided into control group, MS group and MS+telmisartan (MS+Telm) group. Telmisartan was dissolved in 1 ml drinking water at a dosage of 5 mg/kg per day by stomach intubations using a round-ended needle for 6 months. Tail-cuff systolic blood pressure (SBP) was measured. At the end of the treatment period, plasma nitric oxide (NO), superoxide dismutase (SOD) and malondialdehyde (MDA) were detected. Aortic relaxation and contraction were examined using organ bath connecting with polygraphy. eNOS protein and uncoupling protein 2 (UCP-2) expression were measured by Western blot. RESULTS: PE-induced contractile response of thoracic aorta in MS+Telm group was significantly lower than in MS group (P<0.05), whereas acetylcholine (Ach)-induced relaxation response was higher than in MS group (P<0.05). Levels of plasma SOD and NO in MS+Telm group were higher than in the MS group but levels of plasma MDA were lower than in the MS group. Administration of telmisartan significantly increased UCP-2 and eNOS protein expression in aortic rings (P<0.05). CONCLUSION: Telmisartan promotes UCP-2 and eNOS expression in thoracic aorta and effectively improves vascular function in rats with MS.