Human monocytes are important effector cells in host defenses against Aspergillus hyphae, and as elutriated monocytes (EHM) they may be transfused in large quantities to leukopenic patients with invasive aspergillosis. The antifungal activity of EHM against Aspergillus hyphae was compared with that of polymorphonuclear leukocytes (PMNL). The effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) on superoxide anion (O2-) release and on hyphal damage caused by EHM against unopsonized A. fumigatus hyphae was investigated. EHM had antihyphal activity comparable to that of PMNL. GM-CSF significantly augmented O2- release by EHM in response to PMA. Also, both GM-CSF and IFN-gamma significantly enhanced the antifungal activity of EHM compared with untreated controls. Thus, EHM have demonstrable antifungal activity against Aspergillus hyphae that may be increased by GM-CSF and IFN-gamma, suggesting their potential therapeutic role in immune reconstitution of effector cells.