Thirty-eight consecutive patients with Kawasaki disease (18 patients with normal coronary artery and 20 with coronary artery lesions) were studied in order to find the incidence of myocardial abnormalities and the influence of the myocardial damage on the regional wall motion of the left ventricle in patients with Kawasaki disease with or without coronary artery lesion. Abnormal regional wall motion of the left ventricle was found in 28% of the patients with normal coronary artery (NCA) and in 55% of those with coronary artery lesions (CAL). Hypertrophy of myocytes, degeneration of myocytes and disarray were found frequently in the patients with CAL. The histopathology of endomyocardial biopsy taken from patients more than 3 years after disease onset and less than 3 years after onset were compared. Histopathologic abnormalities were found even in the biopsies taken more than 3 years after onset, especially from patients with coronary artery lesions, although the incidence of abnormalities was less frequent. We consider that repeat endomyocardial biopsies may be necessary in the patients who have significant histopathologic changes in the first endomyocardial biopsy to clarify the natural course of myocardial abnormalities, regardless of whether or not they have CAL.