Gastric surgery is still a major part of routine surgical practice. Diagnostic strategies should be oriented to the surgical consequences and their value for our understanding of pathophysiological connections. Endoscopy, perhaps with biphasic radiography, is mandatory for diagnosis of tumor malignity and localisation. Analysis of secretion is indicated in cases of ulcer recurrence. Postoperative syndromes can be detected and classified by scintigraphic methods. The new procedure of endoscopic ultrasonography seems to offer special benefits for diagnostic problems such as gastric lymphoma and other intramural tumors.