We have re-evaluated over-diagnosed cases which were first diagnosed, pre-operatively, as gastric cancer yet later confirmed as benign lesion (excavated lesion, in particular) in the post-operative histological examination of resected stomachs. We have experienced a total number of 1,358 cases which, being detected through mass survey, were diagnosed as cancer and, consequently, operated upon. On the other hand, 61 benign cases were misdiagnosed as cancer, 28 cases being protruded lesions and 33 cases excavated lesions. Among the misdiagnosed cases of excavated lesions, 27 cases were gastric ulcers or their scars, the remaining 6 cases being gastritis or gastric erosion. In 22 out of 33 cases of misdiagnosis, the wrong diagnosis was made by relying solely upon X-ray and endoscopy. Even after the addition of cytology, there were still 9 cases of misdiagnosis. Since, however, biopsy was introduced, there have been only 2 cases of wrong diagnosis. We may safely say that through these findings the absolute necessity of biopsy for the attainment of an accurate diagnosis of early gastric cancer has been sufficiently attested.