Of the first 600 patients to receive aortocoronary bypass grafts 383 had three diseased vessels, and of them 36 (9%) have died: 20 (5%) in hospital and 16 (4%) late. In 10 of those who died, ventricular function was normal, class I or class II and in the other 26 function was class III or class IV. For all ventricular classes except class IV, improvement in myocardial blood flow with operation was considerably lower than average in those who died. The leading cause of late death was congestive heart failure followed by myocardial infarction, and then by other cardiac complications. Of patients with good (normal, classes I or II) ventricular function, 3.5% died during a mean follow-up period of 27 months; and since, according to published reports, 1% of patients with triple-vessel disease without surgical intervention die each month, the data from this study suggest that survival in this group is improved by 23.5%. This study also shows that in patients with triple-vessel disease and good ventricular function, adequate coronary artery bypass operations (i.e., placement of three grafts or more) improves survival.