The acute hemodynamic effects of intravenous nisoldipine were studied in 10 patients with severe congestive heart failure. Nisoldipine was administered in three consecutive doses (1.5, 3.0, and 6.0 micrograms/kg) at least 150 min apart. Following the first dose, mean arterial pressure declined from 96 +/- 17 to 87 +/- 16 mm Hg (p less than 0.01), cardiac index increased from 2.1 +/- 0.7 to 2.4 +/- 0.7 L/min/m2 (p less than 0.025), and systemic vascular resistance fell from 27 +/- 10 to 19 +/- 6 units (p less than 0.01). Maximal hemodynamic effects occurred by 2 to 5 min and gradually waned over the next 120 min. There were no significant changes in heart rate or filling pressures. The time course for the hemodynamic effects were similar with subsequent doses but the magnitude of change was significantly greater. There was a dose-dependent increase in peak arterial nisoldipine concentration. Baseline plasma norepinephrine and renin were high but did not change with nisoldipine administration. No significant changes were seen after nisoldipine administration. No major side effects were observed. These data suggest that nisoldipine is a potent arterial vasodilator that can be of benefit in patients with low output cardiac failure.