We report the pharmacological findings on levofolinate after the intraperitoneal administration of leucovorin-5-FU. Levofolinate 300 mg/saline 500 ml and 5-FU 750 mg/saline 500 ml were administered intraperitoneally over 1.5 h. The plasma and intraperitoneal concentrations of levofolinate at 0, 0.5, 1, 2, 4, 8, 22(20) h after the administration were evaluated at 6 points with HPLC analysis. The intraperitoneal levofolinate concentration went up as high as 100 micrograms/ml and remained above 10 micrograms/ml over 8 hours. This suggested that intraperitoneal administration elevated the portal vein and abdominal lymphatic levofolinate levels. Intraperitoneal levofolinate-5-FU is a promising protocol for gastro-intestinal cancers.