This nonrandomized study compared the results of early coronary artery bypass grafting to those of initial medical therapy in a group of 2,023 patients with severe angina pectoris and 2 major epicardial coronary arteries having greater than or equal to 70% diameter luminal narrowing. Medical therapy was selected for 706 patients, and 1,317 patients were treated by coronary artery bypass grafting. The 6-year survival rate was 76% for patients treated medically and 89% for patients treated surgically (p less than 0.0001). Cox multivariate analysis showed that surgical treatment was a beneficial independent predictor of survival (p less than 0.001). For patients with 2-vessel coronary artery disease who had Canadian Heart Association class III and IV angina at presentation, surgical therapy provided a survival advantage for patients with impaired left ventricular function and proximal narrowing of 1 or more coronary arteries.