He is a council member of the Japanese Gastric Cancer Association and Congress President 90th Annual Meeting of the Japan Gastric Cancer Association. He has served as an associate editor of the World Journal of Surgery. His research interest is to improve outcome for both advanced gastric cancer and minimal invasive function preserving surgery for early gastric cancer. The department treats more than 500 gastric and gastroesophageal malignancies annually. This department has been playing a central role in conducting multi-institutional clinical trials as a member institute for Japan Clinical Oncology Group. Dr. Katai currently has been conducting two trials for laparoscopic-assisted gastrectomy as a principle investigator. He is also carrying several translational studies such as genomic scanning in gastric cancer and DNA methylation as a gastric cancer metastasis risk factor in cooperation with the National Cancer Center Research Institute. This department has an important function for the education of foreign surgeons. More than 20 surgeons from various countries visited this division annually to learn about the management of patients with gastric cancer, especially surgical techniques for lymph node dissection and postoperative care.