We studied the protective effect of human macrophage colony-stimulating factor (M-CSF) of fungal infection due to systemic aspergillosis in normal mice. We also examined the effect of M-CSF against the activities of mouse peritoneal macrophage which were relating to the phagocytosis, the killing, the production of superoxide after contacting with phorbol myristate acetate and the production of nitric oxide after contacting with interferon-gamma in vitro. M-CSF improved the median survival time and the survival rate of systemic aspergillosis. Combination therapy with M-CSF and amphotericin-B (AMPH-B) showed the therapy with either M-CSF or AMPH-B alone. M-CSF enhanced the activities of phagocytosis and the killing of ingested Candida albicans H and spores of Aspergillus fumigatus K by macrophage. Furthermore, M-CSF promoted the production of superoxide and nitric oxide in macrophage. These results indicate that M-CSF can enhance the fungicidal activity of macrophages by activation in vivo, thereby preventing the dissemination of fungal infection.