Fungal infections are the primary cause of mortality in patients with severely impaired host defense mechanisms, such as neutropenic patients with acute leukemia or those who have undergone bone marrow transplantation. In view of the unacceptably high mortality due to disseminated candidiasis, it is rational to focus on augmentation of host defense mechanisms in addition to conventional antifungal therapy. In vitro, a variety of immunomodulators, including tumor necrosis factor, interferon-g, and the hematopoietic growth factors, enhance the killing of Candida albicans, Aspergillus fumigatus, and Cryptococcus neoformans. Various studies have demonstrated beneficial effects of immunomodulatory therapy in animal models of disseminated candidiasis. For further preclinical and clinical studies, recombinant interferon-g, interleukin-1, granulocyte colony-stimulating factor, and the other hematopoietic growth factors are currently the most promising immunomodulators.