The accuracy of the radiologic examination in the detection of gastrojejunal ulcer has been disappointing in that commonly only 20 to 50 per cent of these ulcers have been discovered prior to surgery (30, 32). The clinical diagnosis has depended chiefly on the presence of abdominal pain with or without upper gastrointestinal tract bleeding in patients who have had a previous gastrojejunostomy for duodenal ulcer. Gastrojejunal ulcer is an iatrogenic disease of man, a by-product of the surgical treatment of peptic ulcer. The site is usually in the jejunum, within a few centimeters of a gastrojejunal anastomosis, in which event one may speak of a jejunal ulcer. When the ulcer develops in the junctional region of gastric and jejunal mucosa, the terms marginal and anastomotic are often employed. As used in this report, the designation gastrojejunal ulcer will include all postoperative ulcers in the vicinity of a gastrojejunal anastomosis. The typical postoperative gastrojejunal ulcer is a peptic ulcer. Although knowledge of its pathogenesis is incomplete, peptic ulcer occurs in the presence of active gastric juice (acid and pepsin) and susceptible mucosa. Sandweiss states (27) “We must accept the fact that hydrochloric acid is an important aggravating factor when ulcer is present. Therefore, until new methods have demonstrated superior effectiveness, the medical and surgical regimens will continue to aim at the dilution, neutralization, inhibition or, if possible, elimination of hydrochloric acid. Most patients become symptom free (although not necessarily cured) under such regimens.” Since the introduction of the technics of partial gastrectomy and gastroenterostomy more than seventy-five years ago by Péan (25), Billroth (3), and Woelfler (34), surgery has had an important part in the treatment of peptic ulcer. The usual rationale of the surgical treatment has been the reduction of gastric acid secretion. This is accomplished by excision of acidsecreting gastric mucosa as well as by blocking of either neurogenic or hormonal mechanisms for stimulating gastric secretion. Experience has demonstrated that certain surgical maneuvers are prone to be followed by postoperative ulcers. Gastrojejunal ulceration is likely to occur after operations which drain the duodenal secretions (including liver and pancreatic secretions) into the intestine distal to a gastrojejunostomy (20) or, again, when partial gastrectomy with gastrojejunostomy is done for duodenal ulcer and part or all of the antrum is bypassed and left in situ (1, 10, 29). Also it is generally considered that the resistance of small intestinal mucosa to peptic ulceration is greatest in the proximal duodenum and progressively less in the more distal small-intestine, so that anastomoses between stomach and distal jejunum or ileum are more likely to be associated with ulcers than anastomoses involving the more proximal jejunum (17, 20). Gastrojejunal ulcer is the most common of the major late complications of the surgical treatment of peptic ulcer (14, 26).