Arteriosclerotic aneurysms of the coronary arteries have been noted in 38 patients undergoing cardiac surgical procedures. Age, sex, and risk factors are similar to those in other patients with coronary artery disease. A high incidence of previous myocardial infarction (24 of 38) is related to the frequency of clot formation and embolism associated with such aneurysms. There is also an increased risk of perioperative infarction following coronary artery bypass grafting if the suture line involves the aneurysm wall (6 of 6), but not when sutures are placed away from it. The importance of recognition and proper operative management is stressed.