In certain models of allergic airway disease, mast cells facilitate the development of inflammation and airway hyper-responsiveness (AHR). To define the role of the high affinity IgE receptor (Fcis an element ofRI) in the development of AHR, mice with a disruption of the a subunit of the high affinity IgE receptor (Fcis an element ofRI(-/-)) were exposed on 10 consecutive days to nebulized OVA. Forty-eight hours after the last nebulization, airway responsiveness was monitored by the contractile response of tracheal smooth muscle to electrical field. stimulation (EFS). After the 10-day OVA challenge protocol, wild-type mice demonstrated increased responsiveness to EFS, whereas similarly challenged Fcis an element ofRI(-/-) mice showed a low response to EFS, similar to nonexposed animals. Further, allergen-challenged Fcis an element ofRI(-/-) mice showed less airway inflammation, goblet cell hyperplasia, and lower levels of IL-13 in lung homogenates compared with the controls. IL-13-deficient mice failed to develop an increased response to EFS or goblet cell hyperplasia after the 10-day OVA challenge. We transferred bone marrow-derived mast cells from wild-type mice to Fcis an element ofRI(-/-) mice 1 day before initiating the challenge protocol. After the 10-day OVA challenge, recipient Fcis an element ofRI(-/-) mice demonstrated EFS-induced responses similar to those of challenged wild-type mice. Transferred mast cells could be detected in tracheal preparations. These results show that Fcis an element ofRI is important for the development of AHR after an aerosolized allergen sensitization protocol and that this effect is mediated through Fcis an element ofRI on mast cells and production of IL-13 in the lung.