Therapeutic colonoscopy has replaced or lessened to a significant degree the need or extent of traditional open surgical procedures. The common uses of therapeutic colonoscopy are hemostasis, resection and ablation of benign and malignant disease, decompression and recanalization of obstructed or dilated bowel, as well as foreign body extraction. Bleeding from arteriovenous and other vascular abnormalities can be controlled with 40% to 80% success rates using endoscopically delivered, monopolar, bipolar, or laser coagulation. The palliation of bleeding recurrent or inoperable colorectal cancer is achieved in up to 90% of patients. Virtually all pedunculated adenomas and most sessile adenomas are regularly removed colonoscopically, while large and recurrent villous adenomas in high risk individuals can be successfully managed by endoscopically delivered laser ablation techniques. Emergency colonoscopic reduction of sigmoid volvulus is performed pre-operatively and decompression of the dilated colon of non-obstructive colonic ileus is now regularly achieved. Colonic strictures have been dilated with a variety of techniques ranging from divulsion with through-the-scope balloon dilators to laser recanalization. Pre-operative endoscopic laser relief of tumor obstruction is employed to avoid preliminary or decompressing colostomy. Endoscopic laser debulking and recanalization of recurrent or inoperable cancer has been achieved with up to 80% success and various foreign bodies may be extracted from the colon with a number of endoscopic techniques. The morbidity of therapeutic colonoscopy has ranged from 1% to 2% for polypectomy to 11% for laser palliation of bleeding from advanced cancer, often with obstruction.