We found that the number of peripheral blood polymorphonuclear leukocytes (PMN) dramatically increased in both sarcoma 180 (S-180) and MM-46 mammary carcinoma (MM-46) ascites tumor-bearing mice, and mice required a remarkable resistance to Candida albicans infection via intravenous route. When the resistance was determined by number of cells of C. albicans in the kidney, a significant decrease in the number of fungal cells was observed in the kidneys of infected ascites tumor-bearing mice. An increase of active oxygen levels of PMN from ascites tumor-bearing mice was observed, suggesting that this factor is important in developing of resistance in ascites tumor-bearing mice. Additionally, a culture supernatant of tumor cells co-cultivated with bone-marrow cells in vitro increased the number of granulocytes and macrophages differentiated from the bone-marrow cells.