Twenty four cases with myocardial rupture among 259 patients with autopsy after death due to myocardial infarction, were compared with patients with acute myocardial infarction and death secondary to other causes. Myocardial rupture occured during the first 72 hours in 58% of the patients and all cases within the first five days. Two thirds of the patients were males and 46% were 70 years of age. There were 24 myocardial ruptures (9.5%). Previous history of arterial hypertension and un-remittent anginal pain were predisposing factors for rupture (p=0.05). Other previously reported bad prognostic factors such as persistent hipertension after acute infarction, severe exercise before infarction and history of Diabetes Mellitus were not statistically significant in this study. Ruptured myocardium was not influenced by a previous history of myocardial infarction, hospitalization delay in the C.C.U., administration of anticoagulants, digitalis or pressor amines. There was no significant difference among the groups compared in enzyme curves or magnitude of leucocytosis. Electromechanic dissociation, sinus bradycardia, nodal rhythm followed by idioventricular rhythm and asystole, were observed following myocardial rupture.