Gastrofiberscopy as well as roentgenologic examination of stomach, is now considered to be one of theindispensable diagnostic methods of gastric diseases. In general it is agreed that the roentgenologic examinationis convenient for observation of shape, contour, motor function and gross lesions of stomach whilegastrofiberscopy is especially valuable in detection of mucosal changes or small lesions of stomach. Forevaluation of gastrofiberscopy in the diagnosis of various gastric diseases, the diagnostic accuracy ofgastrofiberscopy was studied in 964 cases who underwent the fiberscopic examination in SNUH during the period fromMarch 1, 1968 till Aprill 30, 1971. The following results were obtained. 1. Each fiberscopic diagnosis in the 964cases was classified as follows; normal stomach 414 cases (42.9%), gastritis 74(7.7%), gastric ulcer 134 cases(13.9%), healed ulcer 14 cases gastric polyp 6 cases (0.6%), leiomyoma 1 case (0.1%), bezoar 2 cases (0.2%) ,xanthoma 1 case(0.1%), gastric carcinoma 237 cases (24.6%), extrinsic mass 1 case(0.1%), post-operative condition9 cases (0.9%), unsataisfactory examination 31 cases (3.2%), indeterminate diagnosis 2 cases (0.2%). 2. In variousgastric diseases, the coincidence rate of diagnosis between fiberscopic and roentgenologic examination was studiedand the obtained results are as follows; in normal stomach 72.9% (302/414), gastric ulcer 69.4%(93/134), healedulcer 42.9%(6/14), benign pyloric stenosis 86.7% (13/15), duodenal ulcer 100.0% (23/23), gastric polyp 66.7%(4/6), gastric carcinoma 87.8%(208/237), post-operative condition 66.7%(6/9). The overall result shows that thediagnostic conicidence between the two methods was observed in 67.7% of the ases (653/964). 3. The diagnosticaccuracy of fiberscopic examination was 85.7%(24/28) in the diagnosis of gastric ulcer, 75.0%(6/8) in thediagnosis of benign pyloric stenosis, and 95.2%(118/124) in the diagnosis of gastric carcinoma. When we includethe cases with benign pyloric stenosis into benign gastric ulcer cases and consider the possibility of falsepositive and false negative errors, the diagnsotic accuracy of fiberscopic examination was 71.4%(30/42) in benigngastric ulcer cases and 77.1%(118/153) in gastric carcinoma cases, respectively. In the 194 cases who underwentsurgical exploration the diagnostic accuracy of fiberscopy was 80.4%(156/194).