Bleomycin was administered to 35 patients with lung cancer (primary lung cancer in 28 cases, metastatic lung cancer in 7 cases), and produced following results. Fibroblast-inhibiting agents were simultaneously administered as multiple combination therapy, "CPBP", with chloroquine, phytonadione, Bleomycin and prednisolone. In consequence, beneficial effect was seen in a fairly large number of cases including small sized lung cancer and terminal cancer cases. In comparison with other antineoplastic agents, Bleomycin had the advantage of not causing hematopoietic disturbances in host. It is considered, however, that the therapeutic efficacy of Bleomycin above mentioned can not be evaluated without prevention of its side effects. Of 67 cases given Bleomycin treatment 10 cases showed fever and 8 cases lung disturbances. Among these side effects lung distur bances rather than hematopoietic disturbances should be kept in mind. In 44 cases of cancer patients who were treated with combination of Blcomycin and a fibroblast-inhibiting agent, chloroquine, lung disturbances were seen in only 4 of them. On the other hand, in 12 cases of malignant lymphoma which were treated without the combined therapy, 4 of them showed lung disturbances-a high rate pulmonary complications than in cancer. In an experimental study of combination of Bleomycin and dextran sulfate inhibition of lung disturbances was observed histologically. And an increase of α and β globulin, triglyceride, seromucoid and fibrinogen was depressed by this combination therapy. This combination therapy also inhibited metastasis by intravenous inoculation of Ehrlich ascites tumor cell in lungs impaired by administration of Bleomycin. It is important that an effective method of preventing side effects of Bleomycin is established so that enough dose of the drug can be admistered.