19 patients in whom cardiopulmonary bypass (cpb) was performed during different types of cardiac operations, developed myocardial failure which remained refractory to inotropic support with increasing doses of adrenaline, dopamine and dobutamine, so that it was impossible to discontinue cpb. After changing the therapeutic approach to a new regime consisting of adrenaline, dopamine and enoximone, low-output syndrome (LCOS) could be successfully reversed in 12 of the 19 patients. In the 7 remaining patients blood pressure dropped in a clinically relevant way under treatment with enoximone. 5 of these patients needed intraaortic balloon pumping (IABP) inspite of the application of enoximone, before cpb could be successfully discontinued. In three patients receiving enoximone, persisting ventricular tachyarrhythmia appeared under treatment, and disappeared after discontinuation of the drug. One patient needed IABP and left heart bypass by means of the centrifugal pump before cpb could be duly discontinued. One patient died intraoperatively due to untreatable right ventricular failure and inability to discontinue cpb. It is concluded that enoximone represents a useful drug in a significant number of patients developing heart failure refractory to inotropic support, on emerging from cpb during cardiac surgery.