A patient with a large posterolateral left ventricular pseudoaneurysm flush with the posterior papillary muscle and associated with mitral regurgitation was successfully treated surgically. The operation consisted of opening the sac of the aneurysm, dissecting the wall of the left ventricle from the fibrous wall of the sac, leaving a cuff of fibrous tissue suitable to hold sutures, and closing the defect with a Dacron patch.