The patient was a 63-year-old male with multiple peritoneal disseminations of advanced gastric cancer. He underwent chemotherapy with a combination of S-1 120 mg/day (3 weeks administration and 2 weeks rest) and cisplatin (CDDP) 60 mg/m(2) (day 8). After 3 courses of this regimen, CT revealed no evidence of ascites. He then underwent laparatomy. Peritoneal dissemination appeared, and the findings were sT3, N0, H0, P1, CY1, M1(PLE), sStage IV. A bypass operation was performed. As second-line chemotherapy, he received combination chemotherapy with S-1 and paclitaxel (PTX) 60 mg/m(2) (div), 20 mg/m(2) ( ip) (day 1, 8). However, he complained of ascites after 16 courses. We tried weekly administration of PTX and tri-weekly administration of irinotecan (50 mg/m(2)) with S-1. This treatment was successfully continued for 20 courses. The adverse effect was anemia (grade 2). He died two years eight months after surgery. The chemotherapy with S-1/CDDP, S-1/PTX, and S-1/PTX/irinotecan was thought to be effective for advanced gastric cancer with peritoneal dissemination.