The case of a 66-year-old man who had rheumatoid arthritis, chronic interstitial pneumonia (IP) with honeycomb lung, and an aortic arch aneurysm is described. He complained of left chest pain in April 1998 and chest computed tomography revealed an enlargement of a thoracic aneurysm whose maximum diameter reached 7 cm. He was urgently transferred to our institution to undergo immediate surgery for an impending rupture of the aneurysm. His PaO2 with 80 Torr with oxygen therapy. The operation included a median sternotomy, extracorporeal circulation with selective cerebral perfusion, the use of cold blood cardioplegic solution, and open distal anastomosis. Although an acute exacerbation of IP occurred 2 months after the surgery, he successfully received intensive care including high-dose steroid therapy and artificial ventilation. He was successfully weaned from the ventilator and is now being followed up with medical treatment.