A Dieulafoy lesion is a term that is used to describe gastrointestinal bleeding caused by rupture of an exposed submucosal artery associated with a minute mucosal defect. The lesion was originally described by Dr Gallard in 1884 and was subsequently characterized by a French surgeon, Georges Dieulafoy, in 1898. Bleeding from Dieulafoy lesions can occur at any age but is most common in elderly men. The typical site of bleeding is the proximal stomach, usually within 6 cm of the cardio-esophageal junction, but bleeding has been described in a variety of other sites including the esophagus, small bowel and large bowel. Most patients present with intermittent and severe bleeding over several days. When bleeding seems likely to be arising from the large bowel, the initial investigation could be either colonoscopy or mesenteric arteriography. The latter is more likely with torrential bleeding. At colonoscopy, techniques that have been used to control bleeding include epinephrine injections, cauterization, clipping and band ligation. The patient illustrated below was a 76-year-old man who presented with massive rectal bleeding. His medical history included bladder cancer, cecal cancer and a previous cerebral infarct. After resuscitation and a blood transfusion, urgent colonoscopy was performed without bowel preparation. A large amount of fresh blood and clots were noted within the bowel lumen and a bleeding point was not identified. Seven days later, colonoscopy was repeated after a further episode of bleeding. Careful inspection revealed an exposed vessel without surrounding ulceration in the distal rectum consistent with a Dieulafoy lesion (Fig. 1). The vessel was ligated with a single elastic band (Fig. 2). Thereafter, bleeding settled and a follow-up colonoscopy showed that the lesion had healed with scar formation. Although rare, Dieulafoy lesions need to be considered in the differential diagnosis of major rectal bleeding, particularly as they are often suitable for endoscopic therapy.