A new dosage format (MMC-CH) of mitomycin C, which is composed of mitomycin C on activated carbon particles, was efficacious for prevention of peritoneal recurrence of gastric cancer. However, it had no such excellent therapeutic effect on the survival of patients with peritoneal dissemination. Out of 50 patients with peritoneal dissemination of gastric cancer treated by intraperitoneal administration of MMC-CH, 4 patients have survived for long periods of time (39-80 months). However, all of the other 50 patients, who did not receive intraperitoneally administered MMC-CH, died of peritoneal carcinomatosis within two years.