ABSTRACTNitroglycerin acts, in part, to reduce arterial impedance, and thus left ventricular work. The reduction in arterial impedance is largely attributable to a fall in systemic vascular resistance, but may also be due to an increased distensibility of the arterial tree. In this study, volume distensibility of forearm arteries was calculated from measurements of pulse-wave velocity before and during intravenous nitroglycerin infusion. Since a fall in blood pressure itself increases arterial distensibility, the induced blood pressure change was controlled as a variable by repeating the measurements with the subject's forearm in a plastic cylinder and repeating the measurements at a variety of altered cylinder pressures. At every studied pressure, nitroglycerin infusion increased forearm arterial distensibility, demonstrating another way in which nitroglycerin reduces left ventricular afterload. Since the pulsatile portion of cardiac work is approximately 10% of total work, the magnitude of this nitroglycerin effect on cardiac function is probably small.