Continuous venous infusion of 5-FU was investigated in patients with advanced gastric cancer under TPN. In preliminary research Yoshida Sarcoma-bearing rats were continuously infused with 5-FU at a dose of 20 mg/kg/day under TPN. The 5-FU level in the tumor was 2-5 times higher than that in the kidney, stomach, intestine and liver, and 40-50 times higher than that in serum. Advanced gastric cancer patients were continuously infused with 5-FU at a dose of 500 mg/day under TPN. Serum 5-FU level was constantly maintained at 0.05 mcg/ml during the infusion period. The effects of 5-FU continuously infused with other anticancer agents and TPN were satisfactory with regard to anticancer response and general condition. In conclusion, in advanced cancer, 5-FU is recommended for use in continuous infusion at a dose of 500 mg/day under TPN.