According to the guide lines of Japan Gastric Cancer Association, the indication has been extended as follow; 1. Mucosal adenocarcinoma, intestinal type, without ulcer. 2. Mucosal adenocarcinoma, intestinal type, with ulcer and 30mm or less in size. 3. Submucosal invaded (SM1, invasion depth was 500 micrometer or less) intestinal type adenocarcinoma, 30mm or less in size. However, the extension for diffuse type adenocarcinoma was not well defined.5000 patients who were treated by gastrectomy were examined and Gotoda reported there were no lymph node metastasis when the cancer was diffuse type, 20mm or less and without ulcer. However, the 95% C.I. was 0-2.6%. Therefore, the extension of the indication for gastric adenocarcinoma, diffuse type is controversial. The aim of this study is to clarify the long term survival of the gastric adenocarcinoma, difuse type, treated by ESD. Patient and methodTo clarify the long term prognosis, gastric mucosal adenocarcinoma treated by ESD from Jan. 2000 to Mar. 2005 was examined in this study. Median observation period was 54 months. The cancers were divided into four groups according to the size of cancer, ulcer scar and histological type. 1. Gastric adenocarcinoma, intestinal type without ulcer, 20mm or less in size (small int., n = 214). 2. Gastric adenocarcinoma, diffuse type without ulcer, 20mm or less in size (small diffuse, n = 7). 3. The other adenocarcinoma, intestinal type (large int., n = 143). 4. The other adenocarcinoma, diffuse type (large diffuse, n = 18). Result: 1. Complications: The perforation rate of small int., small diffuse, large int. and large diffuse was 0.9, 0, 0.7 and 0%, respectively. 2. R0 resection (En bloc and lateral margin was negative) rate was 90.2% (193/214), 100% (7/7), 90.2% (129/143) and 72.2% (13/18), respectively. 3. The local recurrent rate was 0, 0, 0.7% (1/143) and 16.7% (3/18), respectively. 4. Additional gastrectomy rate: 0, 0, 2.1% (3/143), 22.2% (4/18). 3 patients of large int. group were treated by gastrectomy because of the metachronous gastric cancer. And 4 of large diffuse group were treated by gastrectomy because of the risk of lymph node metastasis and 1 patient had lymph node metastasis.5. Prognosis: 24 patients died of the other disease. However, no patients died of gastric cancer. Conclusion1. Complication rate was same in intestinal and diffuse type.2. R0 resection rate in large diffuse group was lower than that of large intestinal group.3. The long term prognosis of small diffuse group was same as that of small intestinal group. Therefore, the indication of ESD could be extended for diffuse type.