Donryu rats with an implanted sarcoma in one hind limb were treated by amputation of the sarcomatous limb and intramuscular administration of Nitromin in one group and by amputation of the sarcomatous limb and regional perfusion of the opposite normal hind limb with Nitromin in another group.

Other groups of similar rats were inoculated with varying quantities of tumor cells in their peritoneal cavity as well as in one of their hind limbs. The tumorbearing limbs were then perfused and serial smears of the ascitic fluid containing tumor cells were examined microscopically.

1. The survival rate of rats, treated by intramuscular chemotherapy after amputation, was markedly lower than that of a similar group treated by regional perfusion of the tumor, even though the dosage of the drug administered was similar in each group.

2. A high survival rate could not be obtained by regional perfusion of the normal hind limb after amputation of the tumor-bearing limb. Death occurred due to metastases unaffected by the perfused chemotherapeutic agent.

3. Tumor cells in the peritoneal cavity markedly decreased in number or disappeared entirely without any direct drug action following regional perfusion of a tumor-bearing limb.

4. The possible role of host immunity acquired after perfusion of a tumor is discussed in relation to its effect on metastases.