Twenty-six patients with acute myocardial infarction (mean delay time 6 hours after onset of symptoms) were randomized to control or nifedipine treatment (10 mg sublingually, followed by 10 mg every 6 hours for a total of 24 hours). Nifedipine reduced arterial blood pressure from 127/78 to 115/70 mm Hg at 30 minutes (p < 0.001) and continued to reduce the blood pressure significantly for 12 to 18 hours. Nifedipine also reduced systemic vascular resistance and the rate-pressure product. Cardiac output increased from 4.9 liters/min before nifedipine to 5.4 liters/min at 60 minutes (p < 0.05 vs controls). In patients with high initial pulmonary wedge pressures, sublingual nifedipine decreased the wedge pressure (p < 0.001) more effectively than did 80 mg of furosemide given intravenously. Thus, nifedipine may be useful in patients with early myocardial infarction and left ventricular failure.