Seventeen patients with chronic obscure gastrointestinal bleeding presenting over a 5-year period are described. While representing only 6 per cent of the total number of admissions due to gastrointestinal haemorrhage they required a disproportionate amount of medical attention, including 67 admissions, 73 radiological and 56 endoscopic procedures and transfusion of a total of 198 units of blood. The diagnoses included 5 cases of recurrent acute upper gastrointestinal erosions, 7 small bowel abnormalities and 4 colonic lesions, with 1 patient undiagnosed. Eight arteriovenous malformations (AVM) were demonstrated angiographically and one Meckel's diverticulum identified by a 99Tcm pertechnetate scan. There were 5 cases in which laparotomy yielded the final diagnosis and in one of these peroperative endoscopy of the small bowel was required. On the basis of our experience and a review of other series, a logical plan of investigation is described for such difficult cases.