Telmisartan is an angiotensin II receptor blocker (ARB) and also an activator of peroxisome proliferator-activated receptor-gamma (PPAR-gamma). We investigated whether telmisartan improves vascular endothelial function in patients with essential hypertension with the production of endothelial nitric oxide synthase (eNOS) through PPAR-gamma.Telmisartan was administered to 15 patients with essential hypertension. To assess vascular function, asymmetric dimethylarginine (ADMA), an eNOS inhibitor synthesized by endothelial cells, and the pulse-wave velocity (PWV) were measured. The serum levels of lipid, glucose, and glycohemoglobin (HbA1c) were also evaluated before and after treatment. Telmisartan therapy significantly decreased the blood pressure and total- and LDL-cholesterol levels. HbA1c was also significantly improved but not in fasting plasma glucose. The serum levels of ADMA were significantly decreased (0.48 +/- 0.08 to 0.42 +/- 0.05 nmol/mL; P = 0.01). PWV values were significantly decreased by telmisartan from 1,822.5 +/- 352.3 to 1,661.5 +/- 299.8 cm/second (P = 0.04*). Telmisartan decreased PWV presumably via the activation of PPAR-gamma, suggesting that this agent improves vascular endothelial function via its pleiotropic effects, a mechanism that is different from its hypotensive effects.