Curative resection is considered to be a standard therapy for gastric cancer with localized peritoneal metastases. For tumors with diffuse dissemination, chemotherapy may play a major role, however, the benefits of reduction surgery and standard chemotherapy have not yet been clarified. Median survival time after reduction surgery was reported to be 4-13 months for patients diagnosed by surgery and/or CT and 5-6 months for chemotherapy for those diagnosed by CT alone. Reduction surgery has a high risk, with a morbidity of 12-44% and a mortality of 3-14%. Palliative surgery should be indicated for stenosis or bleeding due to primary tumors. 5-FU, MTX-5-FU, TS-1, paclitaxel, and their combination are candidates for practice and clinical trials. It is important to evaluate the severity of peritoneal dissemination by diagnostic laparoscopy or laparotomy for decision making.