[en] Japanese men long resident in Honolulu, Hawaii have significantly more ischemic heart disease, but significantly fewer small cardiac scars than men in Hiroshima, Japan. These scars occur in three forms: 1) small scars in the mural myocardium which account for the difference in frequency of small lesions in the two cities, and are of uncertain etiology; 2) areas of diffuse fibrosis in the papillary muscles. These are equally frequent in the two cities, and are associated with advancing age and sclerosis of papillary muscle arteries; and 3) focal scars in the papillary muscles. These are more frequent in Honolulu than Hiroshima. They are healed infarcts due to ischemic heart disease and are associated with a severe degree of extramural coronary artery sclerosis. Small mural myocardial scars, when present, are usually found in multiple sites, and are not related to age at death or heart weight. They are more common in the presence of sclerosis of intramural small arteries, but this association does not explain their more frequent occurrence in Hiroshima. There is no evidence that they are related to A-bomb radiation exposure. (author)