Prostaglandin E1 (PGE1) has been shown to limit infarct size, improve coronary blood flow, inhibit platelet aggregation, and reduce both left ventricular (LV) preload and afterload in experimental animals. Its use in the therapy of patients with acute myocardial infarction (AMI) and congestive heart failure (CHF) has not, however, been reported. Five patients with AMI of less than 12 hours' duration and LV dysfunction were studied to assess the hemodynamic effects of IV infusion of PGE1. PGE1 in the concentration of 0.4 microgram/ml was infused at a rate of 0.003 microgram2kg/min (3 ng . kg-1 . min-1) to a maximum rate of 0.021 microgram/kg/min (21 ng . kg-1 . min-1) for a total time of up to 90 minutes. There was an insignificant increase in heart rate, with significant decreases in mean arterial blood pressure and systemic vascular resistance. Pulmonary capillary wedge pressure declined from 21 +/- 3 to 15 +/ 1 mm Hg (p less than 0.05), mean pulmonary artery pressure and pulmonary vascular resistance decreased (p less than 0.05), mean pulmonary artery pressure and pulmonary vascular resistance decreased (p less than 0.05), with increases in cardiac index from 2.38 +/- 0.08 to 2.89 +/- 0.58 L/min/m2 (p less than 0.01) and stroke volume from 51 +/- 17 to 59 +/- 20 ml/beat (p less than 0.05). No major cardiac or extracardiac side effects were encountered during PGE1 infusion. One patient had transient nausea which did not require discontinuation of the drug. PGE1 is an effective vasodilator and deserves further application in therapy for AMI patients with CHF.