To establish the indications for aortocoronary bypass surgery on coronary artery lesions caused by Kawasaki disease, we analyzed surgical outcome in 26 patients. Ages at operation ranged from 1 to 17 years. All patients were followed up with selective coronary arteriography, thallium myocardial imaging, electrocardiography at rest, and the Master "two-step" and treadmill exercise tests for coronary insufficiency. Surgical outcome was analyzed by comparing results of patient examinations made preoperatively with those both at 1 month and 1 year postoperatively. One month after the operation, 25 (93%) of 27 internal mammary artery grafts and 6 (86%) of 7 saphenous vein grafts were patent; 1 year after the operation, 19 (86%) of 22 internal mammary artery grafts and 6 (67%) of 9 saphenous vein grafts were patent. By comparing the preoperative findings of myocardial imaging with those obtained 1 month after surgery, we found that 17 (68%) of 25 showed improvement and 3 (12%) of 25 were worse. At 1 year, 6 (29%) of 21 showed further improvement than at 1 month, suggesting increased development of the coronary bed after internal mammary artery graft anastomosis. Thus an internal mammary artery graft has proved to be satisfactory in the management of children with coronary artery obstruction caused by Kawasaki disease; it appears that both the quality of life and the life expectancy of those patients can be improved by the surgery.