A 58-year-old man with thoracic aneurysm was admitted because of progressive chest oppression, back pain and the rapidly grown mediastinal mass lesion in his chest X-ray. Aortography and computed tomography revealed impending rupture of saccular aortic arch aneurysm. Emergency operation, consisted of aortic arch replacement under selective cerebral perfusion and CABG with the left IMA, was performed successfully. His postoperative course was uneventful without any neurological deficit. Postoperative angiography demonstrated successful reconstruction of the aortic arch and the patent IMA graft.