Background: Endoscopic laser photocoagulation is commonly used to treat bleeding from the neovascular lesions of chronic radiation proctopathy. The KTP laser is an Nd/YAG–driven unit that emits light with a wavelength of 532 nm. This wavelength of energy is absorbed by hemoglobin and penetrates tissue to a depth of only 1 to 2 mm. Methods: Twenty-three patients were treated with KTP laser and followed for a median of 29 months (range 5 to 51 months); 21 had received radiation for prostate cancer and 2 for uterine cancer. The median age was 77 years (range 68 to 87 years). A median of 2 sessions (range 1 to 5 sessions) was performed using 4 to 10 Watts of power and a median energy of 816 Joules per session (range 204 to 2430 Joules). Results: After treatment there was a significant reduction in the frequency (p = 0.0005) of bleeding, increase in hematocrit level (p < 0.0001), improvement in activities of daily life (p = 0.01), and a reduction in use of health care resources (p < 0.0001). There was a trend toward decreased use of iron supplements (11 to 4 patients) and transfusions (4 to 0 patients). Two patients (9%) developed rectal ulcers after treatment. Conclusions: KTP laser photocoagulation is a safe and effective therapy for bleeding from chronic radiation proctopathy that improves activities of daily living and reduces use of health care resources. (Gastrointest Endosc 2000;52:353–7.)