During the recent 13 years from 1961 to 1973, 21 cases of ulcer-carcinoma satisfying Hauser's pathologic criteria have been found endoscopically, 5 cases (2.6%) of which were mucosal carcinoma accompanying linear ulcer over 30 min in length. In addition, one submucosal carcinoma and 2 cases of sub-early gastric carcinoma, partially invaded into the proper muscle layer, were used for this study. Using these 8 cases and 11 operated ones of benign linear ulcer, we have a comprehensive study of histologic and clinical findings of both groups. As the results, malignant linear ulcer was similar in condition to the benign, either in mother ground or in histologic and clinical findings. Moreover, coexistent carcinoma with all kinds of gastric ulcer and with linear ulcer among them was found in 1.5% and 3.8%, respectively. In a series of controlled group, early gastric carcinoma was found in 2.1% out of 284 cases of no ulcer scar from its follow-up study. Its x2 test revealed no significant difference among these values. However, we might conclude that endoscopical follow-up study of chronic gastric ulcer, especially long linear ulcer, is indispensable for understanding the evaluation of malignant change of ch ronic gastric ulcer.