A patient who developed a prosthetic infection with purulent mediastinitis after replacement of the ascending aorta for acute type A dissection was successfully treated with thoracic transposition of a pedicle of the greater omentum. The patient's further postoperative course was free from infection and, 30 months later, he has not developed any complications from the graft. We consider thoracic transposition of the greater omentum to be an excellent procedure for treating mediastinitis or deep sternal wound infections after cardiac surgery.