Some cases, living a social life in the community, with the old myocardial infarctions found in the mass examinations concerning cardio-vascular diseases (performed by Department of Public Health, Kawasaki Medical School) were analysed for the purpose of finding the factors which regulate incidences and prognoses of the myocardial infarction, and the following results were obtained. 1) The average finding rate of the myocardial infarctions in 8 years was 0.37 % of the examinees. 2) The must conditions for being alive after myocardial infarctions, got from the studies of the 28 cases fond in 1975, were the following. (1) Most of them were attacked in their 50's or 60's. (2) Most of them had serum-cholesterol with normal level. (3) Two thirds of them were engaged in light or hard work. (4) Many of them had proteinuria. (5) They had almost no relation with glycosuria or obesity which had intimate relation with coronary insufficiency.