The proportions of Kawasaki disease patients with cardiac sequelae in Japan were analyzed using nationwide survey data from the 6½-year period July 1982 through December 1988. Of 46 864 cases of Kawasaki disease reported in the surveys, 7637 or 16.3% had cardiac sequelae such as dilation or stenosis of coronary arteries, myocardial infarction, and valvar lesions 1 month on more after onset. The prevalence of cardiac sequelae was particularly high in males, infants younger than 1 year, and children older than 5 years of age. In sequential observation, there was no correlation between the prevalence of cardiac sequelae and periods of high or low incidence of the disease. The prevalence of cardiac sequelae overall declined steadily over the observation period, perhaps as a consequence of increasing use of intravenous gamma globulin. However, children older than the age of 5 years manifested increasing prevalence of cardiac sequelae over the observation period, probably as a result of lower rates of intravenous gamma globulin administration.