Background. Rectal blood loss is a common late sequel of radiation proctitis. Teleangiectasias appear in the mucosa in 2-5%of patients after radiotherapy of the pelvis. Since pharmacotherapy is usually not beneficial, local treatment modalities with formalin irrigation, Nd∶YAG laser and argon plasma coagulation(APC) have been advocated, but experience is still limited. Methods. Between January 1997 and August 2001, 50 consecutive patients with rectal bleeding due to radiation proctitis were included for treatment with APC. Thirteen patients suffered from anaemia, six of whom required blood transfusion. Nine patients were receiving anticoagulant therapy and 10 patients used low-dose aspirin. APC was performed, applying the no-touch spotting technique at an electrical power of 50 Watt and an argon gas flow of 2.0 l/min. Pulse duration was less than 0.5 s. Treatment sessions were carried out at intervals of 3 weeks. Results. In 47 out of 48 patients (98%) in whom the effect could be assessed, APC led to persistent clinical and endoscopic remission of rectal bleeding after a median of three sessions. One patient developed recurrent blood loss after resuming anticoagulant therapy for his aortic valve prosthesis. No adverse effects were encountered after initial treatment. One serious complication occurred in a patient with recurrent blood loss when he was prescribed aspirin for a transient ischaemic attack 2 years after the initial APC. Re-treatment resulted in a major rectal bleeding from a small ulcer with a visible vessel. Conclusions. APC is a safe, effective and well-tolerated treatment for blood loss due to radiation proctitis. The use of anticoagulants and aspirin seems to be a co-factors that induces bleeding. Background. Rectal blood loss is a common late sequel of radiation proctitis. Teleangiectasias appear in the mucosa in 2-5% of patients after radiotherapy of the pelvis. Since pharmacotherapy is usually not beneficial, local treatment modalities with formalin irrigation, Nd: YAG laser Between January 1997 and August 2001, 50 consecutive patients with rectal bleeding due to radiation proctitis were included for treatment with APC. Thirteen patients suffered from anaemia, six of whom required blood transfusion. Nine patients were receiving anticoagulant therapy and 10 patients used low-dose aspirin. APC was performed, applying the no-touch spotting technique at an electrical power of 50 Watt and an argon gas flow of 2.0 l / min. Pulse duration was less than 0.5 s. Treatment sessions were carried out at intervals of 3 weeks. Results. In 47 the of 48 patients (98%) in whom the effect could be ass essed, APC led to persistent clinical and endoscopic remission of rectal bleeding after a median of three sessions. One patient developed recurrent blood loss after resuming anticoagulant therapy for his aortic valve prosthesis. No adverse effects were encountered after initial treatment. One serious complication occurred in a patient with recurrent blood loss when he was prescribed as aspirin for a transient ischaemic attack 2 years after the initial APC. Re-treatment resulted in a major rectal bleeding from a small ulcer with a visible vessel. Conclusions. APC is a safe, effective and well-tolerated treatment for blood loss due to radiation proctitis. The use of anticoagulants and aspirin seems to be a co-factors that induces bleeding.