The results of radiological and endoscopic examination in 1,030 patients were compared. In one third of cases there was some discrepancy relating to a significant diagnostic finding (malignant process, peptic ulcer, polyp, stenosis or deformity, abnormal folds, diverticula or normal findings). In analysing false negative and false positive radiological diagnoses, the patients were divided into two groups (with or without a double contrast technique). Conventional radiography proved ten to 38% less reliable than the double contrast technique for a variety of reasons. In view of the high diagnostic accuracy of modern radiological investigations of the stomach and duodenum, endoscopy and biopsy are recommended as complementary procedures. In addition to the high degree of accuracy of radiological methods for various pathological processes, endoscopy places considerable demands during investigation of the upper intestinal tract. At present radiology is used 19 times as frequently as endoscopy, suggesting that there might have to be a tenfold increase in the capacity of pathological departments if endoscopy is used more frequently.