X-ray findings and gastroscopic findings of patients with primary gastric stump cancer and recurrences of gastric cancer are compared. These findings are compared with the observations of operations. The reasons of false diagnoses and doubtful tentative diagnoses were analyzed. In the analysis of X-ray pictures especially the benign operative caused and the postoperative alterations of the wall and mucosa of the stomach must delimit from infiltrative and polypous increasing tumors. The postoperative control examination may be valuable for the diagnosis, because it gives the possibilities for comparison. Roentgenography in double contrast relieves the diagnosis. Stenosing processes of the cardia and anastomose causes difficulties in differential diagnosis in gastroscopy opposite to scared alterations. The aimed biopsy improves the tumor protection. Both examination techniques shows difficulties in recognition of recurrences, which develop from the duodenal stump. Only a special examination technique leads to an improvement of the results. The instruction and experience of the examiner, the knowledge of tumor diagnostics and of the methods of operations and of the postoperative alterations are for the diagnosis of these processes of decisive importance. X-ray examination and endoscopy are two supplementing examination methods.