Seventeen patients with severe ischaemic heart failure without angina were studied prospectively to determine the effects of surgical revascularization on exercise tolerance, peak oxygen consumption and left ventricular function at rest and during inotropic stimulation at 3 months after surgery. Suitability for surgery was assessed by the presence of ischaemia identified by thallium scintigraphy and stress electrocardiographic (ECG) testing and the left ventricular response to dobutamine measured by radionuclide ventriculography. One patient died awaiting surgery and one required cardiac transplantation. Fifteen patients underwent coronary artery surgery with two perioperative deaths. Thirteen patients were restudied 3 months after surgery. Mean treadmill exercise time (362 +/- 204 s to 562 +/- 303 s, P < 0.05) and peak oxygen consumption (14.9 +/- 3.5 ml/kg per min to 20.8 ml/kg per min, P < 0.01) increased significantly. Resting ejection fraction was not changed after surgery (20 +/- 5% to 21 +/- 6%) but ejection fraction during derived from thermodilution Swan-Ganz catheter data both at rest during dobutamine stimulation were unchanged after surgery. At 13 +/- 3 months after surgery there had been three sudden deaths and one patient had undergone successful cardiac transplantation. Of the remaining nine patients, three had improved to NYHA symptomatic class I, three were in NYHA class II and three in NYHA class III. Repeat treadmill exercise testing in seven patients showed that the improvement in exercise capacity evident in the first follow-up visit was maintained during long-term follow-up.