We studied the acute effects of the calcium antagonist nisoldipine in 10 conscious pigs with chronic heart failure. Left ventricular dysfunction was induced by permanent ligation of the left circumflex coronary artery. Two to three weeks after myocardial infarction the effects of four consecutive 10 min intravenous infusions of nisoldipine (0.05; 0.1; 0.25 and 0.5 micrograms kg-1 min-1) or its solvent on systemic haemodynamics were evaluated. In addition, we used the radioactive microsphere technique to study the distribution of cardiac output after each dose of nisoldipine. Nisoldipine significantly (P less than 0.05) increased heart rate (from 144 +/- 9 to 161 +/- 8 beats min-1), cardiac output (from 2.1 +/- 0.1 to 2.9 +/- 0.2 l min-1), stroke volume (from 14 +/- 1 to 18 +/- 1 ml) and left ventricular dP/dtmax (from 2600 +/- 100 to 3500 +/- 250 mmHg s-1), but had no effect on arterial blood pressure. Left ventricular end-diastolic pressure (from 19 +/- 2 to 16 +/- 1 mmHg) and systemic vascular resistance (from 52 +/- 3 to 37 +/- 3 mmHg min l-1) decreased after nisoldipine. The nisoldipine-induced increase in cardiac output did not affect blood flow to the kidneys, brain, liver or skin, but perfusion of the stomach (84%), adrenals (84%) and normal myocardium (from 200 +/- 25 to 321 +/- 38 ml min-1 100 g-1) as well as infarcted myocardium (from 41 +/- 8 to 61 +/- 19 ml min-1 100 g-1) increased significantly.(ABSTRACT TRUNCATED AT 250 WORDS)