Although clinical and hemodynamic stability predicted outcome very well when left ventricular aneurysm was electively resected in 25 patients (95% survival), more discriminate criteria were essential for 20 patients undergoing urgent operation for severe myocardial decompensation (50% survival). Three methods of ventriculographic analysis primarily sensitive to the function of the non-aneurysmal left ventricle were evaluated. These methods separated patients undergoing urgent operation into a population with high operative risk ( < 18% survival) and a population with low operative risk ( > 82% survival). These criteria also separated 15 patients undergoing operation within three months of myocardial infarction into a group with excellent prognosis ( > 85% survival) and a group with poor prognosis ( < 15% survival). The high operative risk in patients undergoing urgent operation or operation within three months of myocardial infarction, when non-aneurysmal ventricular function is poor, may be too high; it should be undertaken only under unusual circumstances.