Twelve patients underwent surgery for repair of false aneurysms of the left ventricle. The mean interval between the myocardial infarction and the diagnosis was 19 months (range 2 to 80 months). Congestive heart failure was the most common clinical presentation. Most patients had three-vessel coronary artery disease. The false aneurysm was posterior in 10 patients and anterior in two. Three patients with posterior aneurysm had severe mitral regurgitation. Repair was accomplished by resection of the false aneurysm and primary closure of the defect in four patients and by closure with a patch in eight. Nine patients also had coronary artery bypass. Mitral valve replacement was performed in three patients who had severe mitral regurgitation before the operation and in one patient who had severe mitral regurgitation after repair of the false aneurysm and could not be weaned from cardiopulmonary bypass. There were three operative deaths and one additional death after 2 months. All deaths occurred in patients who had mitral valve replacement. Eight patients survived the operation and remained well after a mean follow-up period of 62 months. Patients with false aneurysms of the left ventricle do well after surgical repair, except when concomitant mitral valve replacement is necessary.