The results of aortocoronary bypass grafting in 29 patients with severe left ventricular dysfunction (ejection fraction less than 35%) were studied. All patients had severe angina pectoris; 17 patients has class IV heart function and 12 had class III function according to the New York Heart Association classification. Intra-aortic balloon pump support was instituted preoperatively in all patients. Three patients died in the perioperative period. Survivors were followed up for a mean period of 20 months; there were three late deaths. Sixteen patients were clinically improved; 8 had class I and 8 class II heart function at follow-up. Fourteen patients underwent cardiac catheterization postoperatively at a mean time of 19 months. Although 22 (79%) of the 28 grafts were patent, there was no significant improvement in resting left ventricular dysfunction as assessed by ejection fraction, left ventricular volume or left ventricular end-diastolic pressure. Furthermore, graft patency could not be correlated with improvement in segmental wall motion. There was a 10% operative and an 11.5% late mortality and no measurable improvement in resting left ventricular function in this study but the majority (73%) of the surviving patients experienced definite clinical improvement.