This paper records an experience of 42 cases of cardiac rupture or syndromes simulating rupture. These include free wall rupture, hemopericardium without rupture, septal rupture associated with free wall rupture, pseudoaneurysm, and septal rupture. These groups constitute a series of syndromes with many features in common in terms of clinical presentation, difficulty in assessment, timing of operative intervention, and operative management. Free wall rupture, which can be simulated by hemopericardium without rupture, is not always rapidly fatal. Successful intervention was achieved in six of the 13 cases in the free wall group. Ventricular septal defect occurs less frequently than free wall rupture, is more easily diagnosed, and less frequently requires urgent medical intervention. In 12 of the 14 cases of acute rupture, stabilization of the patient by conservative measures could not be achieved and operation was undertaken within 1 week of infarction. There were seven survivors, in four of whom the defect reopened, with successful reoperation in three. In the remaining 15 cases, stabilization by conservative measures was achieved and operation was delayed until at least 2 weeks after infarction. There were 14 survivors and only one instance of reopening of the defect.