A prospective study of the endoscopic, radiological, and surgical features of chronic duodenal ulceration has been performed. Double contrast barium meal and upper gastrointestinal endoscopy were both performed within five days of elective surgery for chronic duodenal ulceration on 50 patients. The surgical diagnosis correlated with endoscopy in 88% and radiology in 82%, but if both techniques were employed, an accurate pre-operative diagnosis was achieved in 96% of cases. There was poorer correlation in determining the position of the ulcer within the bulb, with only 41% correlation between all three parameters and complete disagreement in 24%. Surgery correlated with endoscopy in 71% but with radiology in only 41%. The correlation between endoscopy and surgery in the diagnosis of duodenitis was only 42%, suggesting that this should be a histological diagnosis. This study suggests that endoscopy is slightly more precise than radiology in the diagnosis of chronic duodenal ulceration, but with a combination of the two techniques almost 100% accuracy can be achieved.