Three patients are presented in whom a subepicardial aneurysm developed as a complication of a myocardial infarction. This aneurysm of the left ventricle is unusual and has 3 distinctive traits: an abrupt interruption of the myocardium that comprises the mouth and typically a narrow neck of the aneurysm; aneurysmal wall comprised of epicardium with or without a thin myocardial layer; and a propensity to rupture spontaneously regardless of the wall components or stage of development. All 3 patients were given a diagnosis using echocardiography and underwent immediate surgical aneurysmectomy. One patient died as a result of renal and respiratory failure postoperatively. The long-term outcome of the other 2 patients was favorable without evidence of additional cardiac rupture or instability.