Gastrointestinal hemangiomatosis is a rare benign vascular lesion, which can produce massive or persistent blood loss. Numerous lesions, usually of the cavernous type, involve stomach, small bowel, and colon. The diagnosis of hemangiomatosis is difficult. It is diagnosed usually by endoscopic study or barium enema for bleeding or anemia evaluation in childhood. A 17-year-old female was admitted to our hospital with anemia and dizziness for several months. She was diagnosed as diffuse intestinal hemangiomatosis by gastroduodenoscopy and colonoscopy. Gastroduodenosocpic findings showed multiple, small, mound-like, reddish-purple hemangiomas on the lower body, fundus and prepyloric area of the stomach. Colonoscopic findings showed similar lesions on the ascending and descending colon. The polypoid lesion on the ascending colon was ligated by detachable snare due to bleeding. No other hemangioma was detected by ultrasonography, abdominal angiography or small bowel series. We report a case of diffuse hemangiomatosis, largely distrubuted in the stomach and colon, but without involvement of skin or other solid organ. The bleeding hemangioma on the ascending colon was treated by endoscopic ligation, and the anemia of the patient was improved. (Korean J Gastrointest Endosc 2004;29:2731)