We established a cancer cachexia model in BALB/c mice bearing Colon 26 and examined antitumor and anticachectic activity of UFT. The mice bearing Colon 26 showed a progressive loss of body weight, loss of lipid, and hypalbuminosis associated with the change of tumor size and these symptoms were improved by removal of cancer. In this model UFT extended life span significantly at 15mg/kg/day though showed a little growth inhibitory activity. UFT showed a significant tumor growth inhibitory activity and extended life span at 20mg/kg/day and could reverse all biological parameters mentioned above. Since the intratumor and plasma contents of IL-6 were significantly lowered in the UFT administered group, it is estimated that the anticachectic activity of UFT originates from reduction of interleukin-6 in tumor.