Background: Radiation-induced proctosigmoiditis is a serious complication of pelvic radiation therapy. Rectal bleeding occurs among 6% to 8% of these patients and is extremely difficult to manage. Pharmacotherapy is generally ineffective, whereas surgical treatment is associated with high morbidity and mortality. Argon plasma coagulation is a new method of noncontact electrocoagulation well suited for hemostasis of large bleeding areas., Methods: From December 1996 through March 1998, we used argon plasma coagulation to treat 28 patients with hemorrhagic radiation-induced proctosigmoiditis. Indications for treatment were anemia (n = 18) and persistent bleeding despite pharmacotherapy (n = 10). Argon flow and electrical power were set at 1.5 L/min and 50 W. The severity of rectal bleeding was graded from 0 to 4 (highest), and hemoglobin levels were recorded before and after treatment., Results: Eighty-two therapeutic sessions were performed (median 2.9 sessions per patient). The severity score for rectal bleeding dropped at least 1 point for all but 2 patients, and the mean value decreased from 2.96 to 0.68. Average hemoglobin level increased 1.2 gm/dL (1.9 gm/dL among anemic patients). No serious complications were observed., Conclusions: Argon plasma coagulation appears to be a simple, safe, and effective technique in the management of hemorrhagic radiation-induced proctosigmoiditis.