A 66-year-old female, who had been taking low dose aspirin for approximately 6 months, was admitted to hospital with severe gastrointestinal bleeding. The source of bleeding could not be demonstrated despite gastroscopy, mesenteric angiography and 99mTc-labelled red blood cell scanning. Mesenteric angiography was repeated, demonstrating a site of bleeding in the proximal small intestine. Laparotomy revealed blood-filled jejunal diverticulosis. Resection of the affected segment resulted in cessation of haemorrhage and the patient remains well in follow up. The present report illustrates a rare cause of gastrointestinal haemorrhage, the possible role of aspirin in causation and the difficulty in diagnosis of bleeding from jejunal diverticulosis.