1. The acute haemodynamic effects of intravenous nisoldipine (1, 2, 4 microg kg(-1)) and nifedipine (2.5, 5, 10 microg kg(-1)) were compared in a randomised, within-patient crossover study. Fifteen male patients with stable angina pectoris treated with atenolol were studied after undergoing routine cardiac catheterisation. 2. Nisoldipine caused a dose-related fall in systemic vascular resistance (maximum 22%) associated with an increase in heart rate and cardiac index (18%) and a fall in mean arterial pressure (7%). 3. By contrast, nifedipine was associated with a significant increase in heart rate but systemic vascular resistance, cardiac index and mean arterial pressure remained unaltered. 4. At doses with equivalent effects on heart rate (2 microg kg(-1) nisoldipine; 10 microg kg(-1) nifedipine) acute dosing with nisoldipine caused a significantly greater fall in systemic vascular resistance and increase in cardiac index, whilst nifedipine caused a greater reduction in stroke volume index and left ventricular stroke work index. 5. The results suggest that, when combined with atenolol, acute dosing with nisoldipine may have a more complementary haemodynamic profile than nifedipine. The implications of this finding for chronic oral dosing in patients with impaired left ventricular function should be evaluated.