Background: In vitro studies indicate that the inflammatory response to zymosan, a fungal wall preparation, is dependent on toll-like receptor (TLR) 2, and that this response is enhanced by the dectin-1 receptor. Complement may also play an important role in this inflammatory response. However, the relevance of these molecules within the in vivo pulmonary environment remains unknown. Objective: To examine pulmonary in vivo inflammatory responses of the lung to zymosan. Methods: Zymosan was administered by intratracheal aerosolization to C57BL/6, TLR2-, TLR4-, MyD88- and complement-deficient mice. Outcomes included bronchoalveolar fluid cell counts. We next examined effects of dectin-1 inhibition on response to zymosan in alveolar macrophages in vitro and in lungs of C57BL/6, TLR2 and complement-deficient mice. Finally, the effect of alveolar macrophage depletion on in vivo pulmonary responses was assessed. Results: Marked zymosan-induced neutrophil responses were unaltered in TLR2-deficient mice despite a TLR2-dependent response seen with synthetic TLR2 agonists. TLR4, MyD88 and complement activation were not required for the inflammatory response to zymosan. Although dectin-1 receptor inhibition blocked the inflammatory response of alveolar macrophages to zymosan in vitro, in vivo pulmonary leukocyte recruitment was not altered even in the absence of toll-like receptor 2 or complement. Depletion of alveolar macrophages did not affect the response to zymosan. Conclusion: Neither complement, macrophages nor TLR2, TLR4, MyD88 and/or dectin-1 receptors were involved in the pulmonary in vivo inflammatory response to zymosan.