Persistence of mucosal gastric carcinomas for 8 and 6 years in two patients. A small gastric carcinoma was detected in a man, but he refused surgery. Eight years later, he was readmitted for a check-up, and a partial gastrectomy was performed. Pathologic examination revealed a well-differentiated adenocarcinoma restricted within the mucosa. In another man, an irregularly shaped, grossly depressed lesion indicating a malignancy was present at the gastric angle, and 6 years later he agreed to a partial gastrectomy. The lesion proved to be a well-differentiated adenocarcinoma confined to the mucosa. Retrospective examination of the original biopsy specimen revealed a small area of adenocarcinoma, presumably overlooked at the initial examination. Thus, some gastric carcinomas of the well-differentiated type can grow at an extremely slow rate, without extensive spread or invasion. Findings in these cases contribute to knowledge of the biological behavior of gastric carcinomas. 