The aim of this study was to introduce an oral rehydration therapy with OS-1 for advanced and recurrent gastrointestinal cancer patients to reduce a hospital stay as well as having a good QOL. We targeted 10 advanced cancer patients. In this study, We recommended the OS-1 drinking amount to be 500 mL to 1, 000 mL whenever the following symptoms were observed:(1) the patient's meal consumption was decreased in half, (2) the volume of urine was decreased, and (3) the frequency of urine was decreased. Nine out of 10 patients were able to drink OS-1 in the range of 500 mL to 1, 000 mL. Most of the patients were taking the chemotherapy along with OS-1 therapy. We confirmed two distinct cases: The patients with OS- 1 short-term drinker at the time of appetite fall because of chemotherapy. Another case was the patients with OS-1 longterm drinkers due to the end of life stage which decreased in meal frequency. ORT with OS-1 may contribute to improve QOL of the terminal patient with chemotherapy.