The prognosis of unresectable advanced gastric cancer patients, especially with wide-spread metastasis in the peritoneal cavity, is very poor. In such cases, only a few treatment methods are available, and chemotherapy as a systemic therapy is often selected. We recently devised an experimental model for wide-spread metastasis in the peritoneal cavity of gastrointestinal cancer, by intraperitoneally implanting colon 26 murine carcinoma PMF-15 cells. When the control mice were autopsied, a number of tumor nodules were formed in their mesenterium, pancreas, liver, etc. and pools of ascites were also occasionally seen. Using this model, oral UFT (combining tegafur and uracil at a molar ratio of 1:4) plus cisplatin (UFTP regimen) prolonged the survival of mice and maintained these mice in relatively better condition than with continuous infusion of 5-fluorouracil plus cisplatin (FP regimen). Since UFT can be used orally, patients receiving UFTP therapy are not required to stay in a hospital for long periods, but rather, are intermittently hospitalized for short periods of time. Better QOL and prolonged survival highlight the potential clinical usefulness of the UFTP therapy.