The value of colonoscopy in the diagnosis and management of lower gastro-intestinal haemorrhage was assessed in 107 patients who were examined during a 2-year period. The main indications were to define uncertain radiological findings, to further investigate the cause of bleeding in patients with normal barium studies and to carry out polypectomy. Radiological lesions were confirmed in 27, defined in 12, and refuted in 14 patients. Twenty-eight lesions were demonstrated on colonoscopy which were not diagnosed by barium enema or sigmoidoscopy. A diagnosis was made by colonoscopy in more than two-thirds of the patients with frank blood loss and normal radiographs. In cases of occult bleeding it was farless helpful. Colonoscopy significantly improved diagnosis and management of gastro-intestinal bleeding when the cause was in doubt after standard investigations. In addition, 37 polyps were removed through the colonoscope from 30 patients.