Rupture of the myocardium following an acute infarction is occasionally compatible with survival. In such cases, pre-existent pericardial adhesions confine the bleeding to a limited space within the pericardial sac and produce a chamber which communicates with the left ventricular cavity. The chamber gradually enlarges and forms a pseudoaneurysm. Two cases are described in which the diagnosis was made preoperatively and the pseudoaneurysm was surgically resected. Twenty-one previously reported cases are reviewed, as well. The condition's progressive nature leading to death from heart failure or rupture of the pseudoaneurysm, and its amenability to surgical cure make it imperative that the diagnostic features be well known. The diagnosis should be suspected in cases of progressive heart failure developing shortly after the acute phase of myocardial infarction, in which chest roentgenograms show an enlarging heart shadow characterized by a distinct posterior or lateral bulge. The diagnosis can be confirmed by left ventriculography, which should be performed immediately in all suspected cases.