Forty early gastric cancers (37 cases) were treated endoscopically by diathermic polypectomy and Nd; YAG laser irradiation. In 23 cases of protruded early gastric cancer, 16 cases were treated by diathermic polypectomy only, 2 cases by Nd; YAG laser only and 5 cases underwent combination therapy with both procedures. Endoscopic treatment was successful in 20 cases, but surgery was performed in two cases with cancerous invasion or lymph vessel infiltration at their cut ends after polypectomy. Local recurrence occurred in a case of submucosal involvement 6 months after combination therapy. In excavated early gastric cancers, 17 lesions of 14 cases were treated by Nd; YAG laser irradiation. Although 13 lesions disappeared successfully after laser treatment, cancers remained in 3 lesions with submucosal involvement after several irradiations. Local recurrence was experienced in a lesion of poorly differentiated adenocarcinoma three months after treatment. In addition, a heat probe unit for hemostasis was applied for endoscopic treatment of early gastric cancer and found to be effective for cancer of the mucosal layer. Among other early gastric cancers, endoscopic treatment is indicated for differentiated adenocarcinomas which are less than 2 cm in size and confined within the mucosal layer.