PERFORATION of the interventricular septum is an uncommon complication of myocardial infarction. Sager1 reviewed 18 cases in a survey of the literature in 1934. Weber2 listed 17 more patients in 1943. Additional reports3 have increased the number of recorded cases of perforation of the infarcted septum to 75, in 28 of which the diagnosis was made ante mortem. It is the purpose of this communication to present two additional cases of myocardial infarction with rupture of the interventricular septum. The first is unusual because of a four-and-one-half-year survival. In the other, in which diagnosis was made during life, the perforation was caused by marked atherosclerotic narrowing of an unusual septal branch of the left anterior descending coronary artery. REPORT OF CASES Case 1.4 —M. R., a 56-year-old white man, was first admitted to the Beth Israel Hospital on Feb. 27, 1931, complaining of increasing dyspnea and cough for eight months.