We measured coronary blood flow by the continuous thermodilution method during coronary sinus catheterization via the femoral vein, and evaluated coronary reserve based on the findings of coronary hemodynamics and myocardial metabolism during atrial pacing. The study subjects consisted of 31 pediatric cases with a history of Kawasaki disease. Among them, 19 had normal coronary angiograms (Group A), 8 had dilated coronary lesions (Group B), and 4 had stenotic coronary lesions (Group C) on selective left coronary angiograms. 1. Coronary blood flow at rest: There were no significant differences between Groups A and B. In Group C, slightly low values were obtained in 2 patients with obstruction or recanalization in the left anterior descending artery. 2. Rate of an increase in coronary blood flow during atrial pacing: It was significantly lower in 5 of 19 patients in Group A, in 2 of 8 in Group B, and in one of 4 in Group C. However, in 2 patients with lower coronary blood flow at rest, the rate of an increase in coronary blood flow during atrial pacing was higher. 3. Following atrial pacing, enhanced anaerobic metabolism was observed in 6 of 17 patients (Group A, 2 of 5; Group B, 2 of 8; Group C, 2 of 4) who showed a poor increase in coronary blood flow during atrial pacing. These results indicate that coronary reserve may decrease even in patients without any coronary sequelae of Kawasaki disease on selective coronary angiograms possibly because of inadequate imaging of the microcirculation, i.e., the problem of the pathologic process at the level of small intramyocardial arterioles. To investigate the coronary sequelae of Kawasaki disease, the evaluation of coronary hemodynamics and myocardial metabolism by coronary sinus catheterization before and after atrial pacing is highly recommended.