Myocardial rupture is found in approximately 20% of fatal infarctions, but the diagnosis is rarely made before death. Rupture occurs in "expanding" transmural infarctions. The diagnosis should be considered in any patient who develops recurrent chest pain and cardiovascular instability within the first week after infarction. Echocardiographic evidence of a dilated infarct with pericardial effusion is confirmatory. Three cases are described, and previous reports are reviewed. Because most patients have multivessel disease, we recommend pericardiocentesis and rapid cardiac catheterization. Infarctectomy may be appropriate when the edges of the lesion are obvious, but the more typical diffuse, serpiginous defects should be closed with dacron-bolstered sutures covered with a wide autologous pericardial patch. Myocardial rupture is a treatable condition, and a high index of suspicion is necessary in order to recognize it more frequently.