Recently, we were unable to use the left internal mammary artery for coronary artery bypass grafting in 2 patients who had undergone successful late correction of coarctation of the aorta. In both patients, the mammary arteries were severely atherosclerotic and calcified; this may have resulted from prolonged and severe obstructive hypertension, which both patients had sustained before repair of the coarctation. Thus, in patients who have undergone late repair of coarctation, a bypass conduit other than the mammary artery may be needed.