Six female patients with radiation cystitis, induced by previous pelvic radiation to uterus cancer, were treated with hyperbaric oxygenation (30-35% of oxygen concentration at 2 atmospheric absolute pressures for 90-120 min daily from 20 to 61 days with the average of 45 +/- 7 days, mean +/- standard error). Except in 1 patient symptoms and cystoscopic findings were improved. No side effects were found. Recurrence of radiation cystitis never occurred during the follow-up period (1.0 +/- 0.1 years). Hyperbaric oxygenation treatment in this pressure environment appears to have a beneficial effect of this disorder.