Yoshida sarcoma-bearing rats were continuously infused with 5-FU at a dose of 20 mg/kg/day, and FT-207 at a dose of 40 mg/kg/day, 100 mg/kg/day or 140 mg/kg/day under TPN. After 4 days, rats were sacrificed and the 5-FU and FT-207 concentrations in their organs were measured. The 5-FU level in the tumor was almost the same at when 5-FU was injected at 20 mg/kg/day and FT-207 at 140 mg/kg/day. This 5-FU level in the tumor was twice and four times higher than that of the group injected with FT-207 at 100 mg/kg/day and 40 mg/kg/day. The 5-FU level in the tumor in all four groups was almost twice as high as that in the stomach, intestine and kidney, 7-10 times higher than that in the liver, and 10-30 times higher than that in serum. The FT-207 levels in the alimentary tract, kidney, tumor and serum were almost the same. The conclusion of our preliminary research is that FT-207 is recommended for use in continuous infusion at 7 times the dose of 5-FU when injected under TPN.