Although endoscopic examination in patients with bleeding of the upper gastrointestinal tract has improved diagnostic accuracy, it has not been useful in predicting clinical outcome and has not been shown to improve the patients' prognoses. This article describes a subgroup of patients with acute upper gastrointestinal bleeding whose clinical outcome can be predicted at the time of endoscopy. In 28 of 317 patients who underwent endoscopy, a "visible vessel" was seen in an ulcer presumed to be the bleeding site. All 28 were later recommended for operation because of recurrent (86 per cent) or uncontrolled (14 per cent) hemorrhage. In contrast, 75 per cent of the remaining 289 patients in whom vessels were not seen, whether or not bleeding from ulcers, had single bleeding episodes managed medically. Since patients with a "visible vessel" can be expected to have uncontrolled or recurrent hemorrhage, surgical treatment should be considered at the time of endoscopy if such a vessel is seen.