In the light of several incidences at Brompton Hospital in which enoximone brought about a striking improvement in cardiac index in patients with refractory left ventricular failure, a study was initiated to compare the effects of enoximone and dobutamine following cardiopulmonary bypass in patients with impaired left ventricular function (pre-operative ejection fraction less than 0.5). In two groups of 10 patients, similar responses of haemodynamic variables were obtained with enoximone or dobutamine administration. In particular, mean cardiac index increased by 25% in the first 15 min and by 60% over the 24-hour study period after bypass. Mean systemic vascular resistance fell by approximately 10%. Mixed venous oxygen saturation increased marginally from a preoperative value of approximately 76% within 15 min of drug administration and then fell and stabilized at about 65% in the next 12 h during re-warming. Patients were weaned from enoximone, after 24 h, without event. Both drugs were shown to produce favourable haemodynamic profiles and to be well tolerated in this relatively high-risk cohort of patients.