Many different chemotherapeutic modalities have been done for patients with peritoneal dissemination of gastric cancer. However, no regimen of chemotherapy has become the treatment of choice for the control of peritoneal dissemination. It is thought that intraperitoneal chemotherapy is effective to contact lesions directly and reduce its side effects. So, many kinds of anticancer agents, including cisplatin, via intraperitoneal administration have been tried for peritoneal dissemination therapy. However, they were not so effective. Recently, intraperitoneal taxane administration has proven very effective for the treatment and local control of severe peritoneal dissemination in gastric cancer. The response rate, including disappearance of as cites, was higher than that of MTX/5-FU systemic chemotherapy. There is no evidence that intraperitoneal taxane is significantly more effective than systemic chemotherapy in gastric cancer. But we considered that intraperitoneal taxane was promising for peritoneal dissemination therapy and organized the Society for the Study of Peritoneal Dissemination in Gastric Cancer. To determine the safety profile and activity of docetaxel via intraperitoneal administration combined with S-1 for gastric cancer patients with peritoneal dissemination, a multi-centric phase I/II study is being carried out now. A phase III study should be conducted in future for further understanding and cooperation in a smoothly undertaken investigation.