A 60-year-old female had undergone laparoscopic oophorectomy for right ovarian tumor. At the time of surgery, peritoneal dissemination and ascites was observed. Histological examination revealed that the resected ovary, peritoneal nodes and floating cells in the ascites were metastatic adenocarcinomas. Later, the primary malignant lesion was found to be a type 4 gastric carcinoma. The carcinoma was judged to be unresectable and treated by combination chemotherapy with TS-1 and CDDP every 6 weeks. After 3 courses of treatments, upper gastrointestinal series and endoscopic examinations were conducted and revealed a marked reduction of the tumor size. No carcinoma cells were detected by endoscopic biopsy. CT-scan showed complete disappearance of metastatic lesions. Staging laparoscopy was performed for evaluation of the effects of chemotherapy, and no adenocarcinoma cells at peritoneal nodes or ascites were found histologically. We performed total-gasterectomy with D1 + alpha lymph node dissection. Histopathologically, resected specimens showed severe fibrosis in most parts of the stomach. Following chemotherapy, the carcinoma was judged to be Grade 2 by histopathological examination.