We report a case of lipomatous hypertrophy of the interatrial septum iii a patient with a recent syncopal episode and shortness of breath. Preoperative transesophageal echocardiography demonstrated a large tumor protruding from the interatrial septum. In addition, the patient was found to have significant coronary artery disease and a right internal carotid artery stenosis. The patient underwent successful resection of the mass with septal reconstruction, aortocoronary bypass, and right carotid endarterectomy. Histology of the mass was consistent with lipomatous hypertrophy. (C) 1998 by The Society of Thoracic Surgeons.