Background High pulse wave velocity (PWV) is related to cardiovascular risk in essential hypertension (EHT). It is reported that short-term treatment with an angiotensin II receptor blocker (ARB) decreases PWV, as well as blood pressure (BP), and increases the serum adiponectin, known as an adipocytokine, which has an anti-atherosclerotic effect. However, it is not known whether long-term treatment with ARB prevents the increase in PWV independently of the reduction of BP, and whether adiponectin is related to the chronic effect of ARB on PWV. Methods and Results In order to examine the short-term effect of ARB on PWV, 9 subjects with EHT had PWV measured before and after treatment with an ARB for 1 month. The treatment significantly reduced PWV and BP. For evaluation of the long-term effect of ARB therapy, 56 consecutive subjects with EHT who were already taking anti-hypertensive drugs other than an angiotensin-converting enzyme inhibitor had their PWV measured. We divided the EHT subjects into 2 groups: (1) the ARB group (EHT treated with an ARB for at least 6 months) and (2) the control group (EHT treated with anti-hypertensive drugs other than an ARB). Although there was no significant difference between the 2 groups in BP, age or body mass index, the PWV value in the ARB group was significantly lower than that in the control group. Moreover, the serum adiponectin concentration in the ARB group was significantly higher than that in the control group. Conclusions Long-term treatment with ARB inhibits the progression of arterial stiffness independent of BP reduction. One of the mechanisms may be related to the increased serum adiponectin concentration after treatment with an ARB. (Circ J 2004; 68: 1194 - 1198)