Immediately before closing the abdomen in a curative operation for colorectal cancer, 20 mg of Mitomycin C (MMC) was administered by intravenous, intraperitoneal or intrapelvic routes, and portal blood and peripheral blood were simultaneously collected to investigate the disposition of MMC. After intravenous administration, the MMC concentration in portal and peripheral bloods changed at the same levels, showing a biphasic pattern. The maximum concentration (Cmax) seen shortly after administration was about 2 micrograms/ml. The blood halflife in phase alpha was about 5 min, and that in phase beta about 30 min. After intraperitoneal administration, the MMC concentration in portal blood was over 60 min higher than that in peripheral blood. Cmax in portal blood, seen within 5 min after administration, was about 0.5 micrograms/ml, and that in peripheral blood was about 0.2 micrograms/ml around 10 min. The half-life was about 30 min in both types of blood. After intrapelvic administration, the MMC concentration in portal blood changed at higher levels than in peripheral blood, as after intraperitoneal administration. The Cmax in portal blood, obtained within about 5 min, was about 0.3 micrograms/ml, and that in peripheral blood was about 0.1 micrograms/ml at 12 min. The half-life was about 30 min in both types of blood. As described above, the disposition of MMC was investigated on the basis of the concentration in portal and peripheral blood. As a result, intravenous MMC showed a similar change, whereas intraperitoneal or intrapelvic MMC was higher in portal blood than in peripheral blood, indicating that the disposition of MMC was different with the route of administration.