Telmisartan, a new angiotensin II type 1 receptor blocker (ARB), was recently reported to stimulate PPARgamma, and stronger effects of Telmisartan on insulin sensitivity has been expected than the class effect of ARB. In the present study, we examined the effects of Telmisartan on insulin sensitivity and adipokine levels in hypertensive and type 2 diabetic patients. Outpatients with both hypertension and type 2 diabetes mellitus (n=36; male 23, female 13), received 20-40mg Telmisartan orally once daily for 6 months. Physical examinations and blood or urine tests were performed before and 3 or 6 months after starting Telmisartan treatment. Results were statistically compared using Wilcoxon analysis. Telmisartan treatment for 3 or 6 months reduced systolic and diastolic blood pressure and urinary albumin excretion. Fasting plasma glucose, HbA1c, total and HDL-cholesterol, triglyceride, body weight, BMI and waist length were not changed. Fasting IRI and HOMA-IR were significantly decreased after Telmisartan treatment, suggesting the improved insulin sensitivity. Total and high molecular adiponectin were not changed. Interestingly, serum leptin was significantly increased by 3 months Telmisartan treatment, suggesting a possible involvement of leptin in improved insulin sensitivity. In conclusion, Telmisartan improved insulin resistance with increased serum leptin level in hypertensive and type 2 diabetic patients.