Radiation proctitis is a common complication of radiotherapy for pelvic malignancy. In the more severe form, it leads to intractable or massive hemorrhage, which may require repeated hospital admissions and blood transfusions. Medical therapy in patients with radiation proctitis is usually ineffective, whereas surgery is associated with a high morbidity and mortality. Eight patients (seven females and one male) with hemorrhagic radiation proctitis were treated over a six-month period with endoluminal formalin. The technique used ensured minimal contact with formalin. The median age of the patients was 68 years (range, 42-73 years). Seven patients had had cancer of the uterine cervix, and one patient had had cancer of the prostate treated with radiotherapy at a median time of 30 months (range, 9-46 months) previously. The median duration of time of symptomatic rectal hemorrhage before formalin therapy was eight months (range, 1-12 months). The median number of units of blood transfused previously per patient was four (range, 2-32). The time taken for formalin therapy was 20 minutes (range, 10-70 minutes). One patient required repeat formalin application at two weeks. Bleeding ceased immediately in seven patients after formalin treatment. No further bleeding was noted, nor was any blood transfusion needed, at follow-up at four months (range, 1-6 months). Formalin therapy is a simple, inexpensive, and effective treatment for hemorrhagic radiation proctitis.