Zygomycetes cause serious invasive infections, predominantly in immunocompromised and diabetic patients with poor prognoses and limited therapeutic options. We compared the antifungal function of human polymorphonuclear leukocytes (PMNLs) against hyphae of Rhizopus oryzae and R. microsporus the most frequently isolated zygomycetes, with that against the less frequently isolated Absidia corymbifera. We then evaluated the effects of interferon (IFN)–γ and granulocyte-macrophage colony-stimulating factor (GM-CSF), alone or combined, on PMNL antifungal function against these zygomycetes. Both PMNL oxidative burst in response to hyphae and PMNL-induced hyphal damage were significantly lower in response to Rhizopus species than in response to A. corymbifera. Incubation of PMNLs with IFN-γ and GM-CSF alone or combined for 22 h increased the PMNL-induced hyphal damage of all 3 species. The treatment of PMNLs with the combination of IFN-γ and GM-CSF significantly increased the release of tumor necrosis factor–α in response to R. microsporus and A. corymbifera hyphae. IFN-γ significantly reduced interleukin-8 release in response to all zygomycetes. Although Rhizopus species demonstrate a decreased susceptibility to the antifungal activity of human PMNLs, in comparison with A. corymbifera IFN-γ and GM-CSF augment the hyphal damage of all 3 zygomycetes, suggesting a role for IFN-γ and GM-CSF in the management of invasive zygomycosis