To observe the secular trend of a proportion of Kawasaki disease patients with cardiac sequelae in Japan, we analyzed patients with Kawasaki disease reported to nationwide surveys of the disease during 10.5 years from July 1982 to December 1992. Of 69,382 patients reported to the surveys, 10,596 (15.3%) were reported to have cardiac sequelae such as dilatation or stenosis of coronary arteries, myocardial infarction or valvar lesions, 1 month or more after onset. The percentage of cardiac sequelae was particularly high in males, infants younger than 1 year and children older than 5 years of age. The overall prevalence declined steadily over the observed period. However, the percentage for children older than 5 years of age did not decrease, whether treated with intravenous gamma globulin or untreated. As a consequence of the increased number of patients treated with intravenous gamma globulin, the proportion of Kawasaki disease patients with cardiac sequelae decreased annually. However, the proportion of children older than 5 years of age did not decrease.