Background: The nasal epithelium is the first barrier encountered by airborne allergens and is an active participant in airway inflammation. Fungi have been increasingly recognized as important pathogens in sinusitis and airway diseases. The aim of the study was to evaluate fungal protease activity during cytokine production in nasal polyp epithelial cells and to determine the expression of Toll-like receptor (TLR) mRNA by fungi. Methods: Nasal polyp epithelial cells were obtained from patients and stimulated with Alternaria and Aspergillus. Interleukin-8 (IL-8) and granulocyte macrophage colony-stimulating factor (GM-CSF) were measured to determine the activation of epithelial cells. Reverse transcriptase polymerase chain reaction for the TLR mRNA expression of the nasal epithelial cells was performed. Cytokine production was inhibited with protease inhibitors and anti-human TLR antibodies. Results: The fungi enhanced the production of IL-8 and GM-CSF from nasal epithelial cells. When nasal epithelial cells were activated by the fungi, TLR2, TLR3 and TLR4 mRNAs were more strongly expressed than in the nonactivated cells. Cytokine production was inhibited by protease inhibitors and anti-human TLR4 antibodies. Conclusions: The results of this study showed that fungi interacted with nasal epithelial cells and enhanced the production of cytokines and TLR mRNA expression. The cytokine production was related to the protease in fungi and TLR4.