The 20-year clinical outcome is excellent for the children with Kawasaki disease who underwent a bypass operation using the internal thoracic artery. This operation is feasible from 1 year-old children and in our experience with more than 110 patients, the operative and hospital mortality was 0%, and the 20-year survival was 98.4%. The recent patency rate was nearly 95% for the internal thoracic artery graft regardless of the patient's age, and the 20-year patency was 87.1%. Moreover, the wall characteristics of the internal thoracic artery was quite smooth and apparently well adapting to the somatic growth of children over 20 years after the operation. In contrast, vein grafts had a lower patency of 57% at 20 years. In addition, patent vein grafts showed irregularity of the wall and in some, atherosclerotic changes were observed. Pediatric coronary bypass operation utilizing the internal thoracic artery is proved to be a golden standard treatment modality for complicated coronary artery obstructive disease due to Kawasaki disease, based upon the 20-year clinical and angiographic follow-ups.