From October 1969 through March 1972, 1,276 patients underwent coronary artery bypass at the Texas Heart Institute. Associated conditions included simultaneous valve replacement and resection or repair of ventricular aneurysms or ascending aortic aneurysms. Among the series were 1,105 patients who underwent bypass surgery alone, with or without endarterectomy. Factors affecting outcome were analyzed and revealed adverse influences including concomitant endarterectomy, female sex, age, evidence of left ventricular failure or serious ventricular dysfunction, and previous myocardial infarction within the month before surgery, but more importantly within the week prior to surgery. Functional class III and IV angina was significantly decreased or totally relieved in a high percentage of patients after bypass surgery, and remains the major indication at this time for myocardial revascularization. Progressive reduction in surgical risk and improvement in patient selection allow coronary artery bypass to be performed currently with an early mortality risk of only 3.7%.