Acquired perforation of the infarcted interventricular septum is a rare condition which is infrequently diagnosed. The only reported case in which an antemortem diagnosis was established is that of Brunn in 1923. The purpose of this report is to present another case of this complication of coronary thrombosis and to review the subject completely. I shall also attempt to present the criteria which make this condition, rare as it is, one that is clinically easily recognizable. Krumbhaar and Crowell,1in 1925, gathered from the literature 654 cases of nontraumatic rupture of the heart, almost all secondary to coronary occlusion. At present the total is well over 700. From these figures it is evident that rupture of the heart is not rare. However, there are recorded only 17 cases of perforation of the infarcted interventricular septum, or nearly 3 per cent of all reported nontraumatic ruptures of the heart. With the