The purpose of our study was to determine differences in coronary lesions after myocardial infarction between Japan and Western countries. One hundred ninety-two patients under 69 years of age admitted to our CCU were diagnosed as having an acute myocardial infarction. One hundred thirty of 153 surviving patients received coronary arteriography, and 12% had zero-vessel, 42% single-vessel, 25% two-vessel and 12% three-vessel coronary artery disease. Of 113 patients without a previous history of myocardial infarction, 12% had zero-vessel, 44% single-vessel, 27% two-vessel and 17% three-vessel disease. We compared these results with the reports of three similar studies from Western countries. The percentage of multivessel patients in our study was the lowest among the four studies (p less than 0.05). Coronary lesions in patients without a previous history of myocardial infarction differ from reports in the United States (p less than 0.05). These results may suggest that we should carefully evaluate the reports of secondary prevention for chronic myocardial infarction, considering the different severity of coronary lesions in each country.