In 39 patients with coronary artery disease and angina pectoris, exercise hemodynamic evaluation, left ventriculography, and coronary arteriography were performed both before and 3 to 36 months (mean 17 months) after aorta-coronary artery bypass grafting. Of the 32 patients with abnormal exercise hemodynamic responses before operation, 11 returned to normal at the postoperative study (Group N) and 21 remained abnormal (Group A). Preoperative characteristics (mean age, functional class, prior myocardial infarction, left ventriculographic appearance, mean ejection fraction, and mean number of vessels diseased) were similar in the two groups. Of the perioperative and postoperative characteristics examined (mean number of grafts, operative myocardial infarction, postoperative functional class, treadmill test result, and adequacy of left coronary artery revascularization), only the adequacy of left coronary artery revascularization differed between Groups N and A. Eight of 11 Group N and only three of 20 Group A patients had complete revascularization, with patent grafts, of the left coronary artery. We conclude that improved exercise hemodynamic function does occur in some patients after aorta-coronary artery bypass operations. Such improvement is most likely when all major lesions of the left coronary artery are completely revascularized.