Blood pressure, volume distensibility (VD), and cross-sectional area (CSA) of the brachial artery were studied using pulsed Doppler systems in 51 patients with sustained essential hypertension in comparison with 21 normotensive controls of the same age. In hypertensive patients, in baseline conditions, CSA was significantly increased and VD decreased--the two parameters strongly and negatively correlated independent of the blood pressure level. Arteriolar vasodilatation was produced by three pharmacological agents--cadralazine, a dihydralazine-like compound; nicorandil, a nicotinamide derivative; and nitrendipine, a calcium entry blocker. For the same blood pressure reduction, cadralazine significantly reduced CSA, while nicorandil and nitrendipine increased it. Nitrendipine significantly increased VD, which was not modified by cadralazine and nicorandil. For cadralazine and nicorandil, a significant negative correlation was observed between VD and CSA. The relationship was the same as in baseline conditions. With nitrendipine, no significant correlation was observed between the two parameters. At any given CSA, distensibility was higher with nitrendipine than with cadralazine or nicorandil. The study provided evidence that, in men with essential hypertension, in basal conditions, the negative relationship between VD and CSA reflected intrinsic alterations of the arterial wall, while cadralazine, nicorandil, and nitrendipine caused a similar degree of arteriolar dilatation, nicorandil and nitrendipine caused active arterial dilatation as well, and changes in distensibility after drug administration were not directly related to blood pressure level and were mediated either by predominant geometrical modifications (cadralazine, nicorandil) or by the predominant relaxing effect of the drug on arterial smooth muscle tone (nitrendipine), or both.