Studies on iron metabolism, especially on organ iron were performed in mice with Bashford cancer treated by combined administration of chloroquine and several anti-tumor agents. 1) Chloroquine alone tended to inhibit the storage of non-hemin iron in the tumor tissues or organs. 2) No definite tendency was shown in the storage of non-hemin iron following administration of anti-tumor agents alone. 3) Generally, it was difficult to find a definite tendency in organs such as the liver and spleen after combined administration, but in the tumors the storage of non-hemin iron (γ/g) tended to be more inhibited by combineda dministration than in controls and in mice treated by anti-tumor drugs alone. 4) These data suggest that the combined chemotherapy with choroquine and several antitumor drugs exhibits more effective anti-tumor activity with respect to iron metabolism of animals bearing Bashford cancer than single administration of anti tumor drugs.