The accuracy of gastrofiberscopic biopsy in diagnosis of gastric malignancies has been evaluated by studying operative and postmorten findings and clinical follow-up data in linkages at Osaka Cancer Registry, Japan, after an average of 7.7 years. Satisfactory data were obtained in follow-ups of all 1331 patients examined. There were only 31 (3.7%) false-negative diagnoses of malignancy among 858 patients diagnosed as having benign lesions, and only three (0.6%) false-positive diagnoses among 473 patients diagnosed as having malignant tumors. The false-negative diagnoses were most frequent in cases of elevated types of early cancer, advanced cancer of type 4 and leiomyosarcoma, or in cases located in the posterior wall and in the antrum. The three benign lesions that were diagnosed as malignant by biopsy were all associated with active ulceration, indicating that care is necessary in taking biopsy specimens of ulcerated lesions. From these findings the sensitivity and specificity of the gastrofiberscopic biopsy method for detection of gastric malignancies were calculated to be 93.8% and 99.6%, respectively, and the overall accuracy for all the patients was 97.4%. These results reconfirm that gastrofiberscopic biopsy is very useful for diagnosis of gastric malignancies.