Optimal regimens for the treatment of invasive fungal infections have yet to be defined, and these life-threatening conditions are one of the leading causes of treatment failure in patients with cancer. A substantial body of preclinical work points in the direction of using cytokines as immunomodulators of the multiple deficiencies involved in the progression of fungal infections in neutropenic and nonneutropenic cancer patients. These deficiencies include not only the easily recognized deficiencies in cell quantity but also subtle deficiencies of cell function. Four cytokines (granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, macrophage colony-stimulating factor, and interferon gamma) show promise as adjuvant therapy for proven fungal infections in this setting, although clinical experience is still limited. As an additional approach, the concept of white blood cell transfusions has been revived by the use of granulocyte colony-stimulating factor and promises to be helpful in the setting of neutropenia.