Hyperbaric oxygen therapy was performed in 6 cases (female) of x-ray ulcer following radiotherapy for breast cancer, esophageal cancer, uterine cancer, and rectal cancer. The exposed dose ranged from 4500 to 7500 R, and x-ray ulcer occurred after one to twelve years of the irradiation. The mixed intravenous instillation composed of 1200 mg of Glutathione, 1 g of VC, and 6000 unit of Uronase was performed before the performance of the hyperbaric oxygen therapy. This therapy was carried out once a day for 20 days (one period), and was suspended for one to two weeks between periods. It was carried out for about four periods. Furthermore, antibiotics and local ointment were used. Disappearance of ulcer was recognized in 5 of 6 cases, and the recurrence has not been found out for 4 years. One case, the rest, was given Cytorevie, and did not receive this therapy from his will.