The effects of milrinone, a phosphodiesterase III inhibitor, were studied in patients with heart failure following coronary artery bypass grafting. Twenty patients with heart failure (either a cardiac index of less than 2.0l/min/m² or a pulmonary capillary wedge pressure of greater than 12mmHg) were divided into two groups according to whether or not they received postoperative milrinone administration. The control group (n=10) received no milrinone treatment and the milrinone group (n=10) received intravenous milrinone infusion at a speed of 0.5μg/kg/min postoperatively. The hemodynamic measurements were made perioperatively and clinical results were accessed perioperatively. Within-group comparison revealed a marked (p<0.05) decrease in pulmonary capillary wedge pressure and systemic vascular resistance in the milrinone group. Cardiac indices were significantly (p<0.05) greater in the milrinone group than those in the control group and within-group comparison revealed a significant (p<0.05) increase in left ventricular stroke work index in the milrinone group. There was no significant difference in rate pressure product in between- and within-group comparison. The milrinone group had a significantly (p<0.05) lower temperature difference between the rectum and the sole, and significantly (p<0.05) less catecholamine requirements postoperatively. Milrinone was not associated with a significant increase in the prevalence of adverse effects. The results suggest that milrinone possesses positive inotropic and vasodilatory effects in patients with heart failure following coronary artery bypass grafting. In addition to catecholamines and vasodilators, milrinone may become a useful agent in the treatment of patients with postoperative heart failure.