During 23 years, 224 cases underwent graft replacement of thoracic aortic aneurysms at our institution. Of these, 14 cases suffered postoperative vascular graft infection. Out of the 14 cases, 13 cases had sternal or mediastinal infections, and one case showed sepsis without these deep wound infections. Six cases were positive by blood culture. We thought that sternal or mediastinal infections had a high possibility of contamination of vascular grafts and that cases with these deep wound infections should be treated as cases of graft infection. Reoperation was done urgently soon after the diagnosis of infection was made. When the wound was not so deep, only debridement was performed. In addition to debridement, continuous irrigation through a chest tube and, recently, pedicled omental flap placement were done, when the wound was deep. Except for the one case without deep wound infection, 13 cases were reoperated. There were 4 hospital deaths; 3 operated cases and the nonoperated case, due to lack of control of their infection. Blood culture were positive in all these four cases. The other 10 cases were discharged from hospital without infection. Infection of vascular grafts after operation for thoracic aortic aneurysms is a serious complication and urgent reoperation should be done. However it should be noted that the mortality rate of cases with positive blood culture is high.