Tumor-bearing mice showed a significant resistance against Candida albicans intravenous infection. Longer survival was observed in groups of mice inoculated with fungal cells 2—3 weeks after tumor transplantation with allogeneic sarcoma 180, syngeneic methylcholanthrene-induced Meth A fibrosarcoma, and MM 46 mammary carcinoma than in non-tumor-bearing mice inoculated only with fungal cells. This effect was not observed when the mice were infected only 1 week after tumor transplantation. A significant decrease in the number of C. albicans cells in the kidneys was observed in mice inoculated with fungal cells 2—3 weeks after tumor transplantation. In the tumor-bearing mice treated with cyclophosphamide (CY), a remarkable decrease in both the number of peripheral blood polymorphonuclear leukocytes (PMNs) and the defense against challenge with C. albicans cells was observed, as compared with the CY-untreated groups (normal and tumor-bearing mice). A marked increase in the calcium concentration in serum and number, candidacidal activity, active oxygen level, and myeloperoxidase activity of PMNs was observed in the 2—3-week tumor-bearing mice. From these results, it is suggested that PMNs, which accumulated in the 2—3-week tumor-bearing mice, play an important role in the protection from C. albicans infection by increasing the number and the types of killing factors.