Forty two patients were studied prospectively by rest and exercise radionuclide ventriculography before and after (10 +/- 4 months) left ventricular aneurysm resection. Functional classification (NYHA) improved from 3.0 +/- 0.6 to 2.3 +/- 0.5 (p less than 0.0001) with an increase in double product (p less than 0.01) and total exercise workload (p less than 0.04) over preoperative values. End-diastolic volume was significantly reduced (p less than 0.0001) and resting global left ventricular ejection fraction (LVEF) improved significantly (p less than 0.03) after surgery, as did regional ejection fractions of the lateral/inferior wall (p less than 0.01). Cardiac index (CI) at rest, however, remained unchanged. Under exercise, improvement of global (p less than 0.0003) and regional ejection fractions (p less than 0.02) was more pronounced and a significant increase was also observed for CI (p less than 0.003). Improvement in left ventricular performance occurred both in patients with single and multiple vessel disease, but was more distinct in the latter group who additionally received coronary artery bypass grafts. These patients were furthermore postoperatively able to increase global LVEF at exercise (p less than 0.05). We conclude that aneurysm resection with or without coronary bypass relieves cardiac symptoms and improves exercise tolerance and left ventricular function at rest and on exercise in most patients.