Between January, 1971, and June, 1981, 278 patients undergoing coronary artery bypass grafting had additional endarterectomy to the left coronary system. This constitutes 28% of all patients undergoing bypass grafting. Additional endarterectomy of the left anterior descending was performed in 250 and of the circumflex in 75 (an average of 1.2 endarterectomies to the left coronary system per patient). Five hundred thirty-six additional grafts to other vessels were performed, for a total of 861 grafts (three grafts per patient). There were 11 (4%) early and 29 (10%) late deaths. The actuarial survival rate was 93% at 3 years and 80% at 6 years. The incidence of perioperative myocardial infarction was 12%. Of the survivors, 94% were either asymptomatic or improved. Two hundred forty-three grafts (75%) were restudied early (2 weeks to 1 year). The early patency rate of the grafts to the left anterior descending was 83% (156/188) and to the circumflex 75% (41/55). In 75 patients (81 grafts), restudied 1 year or more after operation, the patency rate was 75% (61/81). The runoff of grafts to the left coronary system was judged to be good in 76%, moderate in 14%, and poor in 10%.