The clinical characteristics of 30 cases of myocardial rupture resulting from acute myocardial infarction were analyzed. Predisposing factors of myocardial rupture appeared to be the following (1) age 60 years or older, (2) female, (3) no previous history of angina or myocardial infarction, (4) hypertension on admission, (5) persistent or recurrent chest pain, (6) physical activity and/or emotional unrest, (7) less than 10 days since the onset of myocardial infarction. From 1979 to 1982, we tried to eliminate these risk factors in the acute stage of myocardial infarction, of which hypertension appeared to be the most important and main correlating factor. The incidence of myocardial rupture before elimination of risk factors was 31.2% (26 of 84 patients) which was reduced to 8.8% after elimination. In the years 1981 and 1982, only two cases of myocardial rupture were found in each year, 4.3% and 5.6% of MI patients, respectively.