Apart from lowering blood pressure, antihypertensive drugs may influence vessel wall function. In a randomized double-blind study, the effect of lisinopril and metoprolol on arterial distensibility was studied in 40 patients with essential hypertension. After a placebo run-in period, the patients were randomly treated with metoprolol (50, 100, or 200 mg) or lisinopril (5, 10, or 20 mg) for 10 weeks. In the lisinopril group, blood pressure decreased after 10 weeks of therapy from 173±10/102±5 to 155±10/85±3 mm Hg and in the metoprolol group from 167±12/102±4 to 153±8/84±3 mm Hg. Diameter (millimeters), relative change in diameter (percent), and distensibility (10−3/kPa) of the left common carotid artery were determined after the placebo run-in period and after 6 and 10 weeks of antihypertensive therapy. A multigate Doppler system was used to measure the vessel wall movements by Doppler analysis in M-mode; blood pressure was recorded by finger plethysmography (Finapres). Neither lisinopril nor metoprolol influenced the end-diastolic diameter of the common carotid artery after 6 and 10 weeks of treatment. In the lisinopril group, a significant increase of percent change in diameter (P<.05 compared with the baseline value; P<.05 compared with the metoprolol group) and distensibility (P<.01 compared with the baseline value; P<.05 compared with the metoprolol group) was observed. The results show that lisinopril but not metoprolol improves arterial distensibility in essential hypertension. Pressure-independent effects of angiotensin converting enzyme inhibitors may be important modulators of adaptive changes in the arterial wall.