Incorporation of multi-wall carbon nanotubes (MWCNT) into materials has raised concerns about their potential hazards to manufacturing workers. In animal models, airway inflammation and lung fibrosis follow aspiration, instillation, and inhalation exposures to MWCNT. However, the effects of MWCNT on pulmonary function, airway reactivity and airway epithelium function following inhalation exposure has not been studied. We investigated whether inhaled MWCNT affects lung resistance (RL) and dynamic compliance (Cdyn), reactivity to inhaled methacholine (MCh), epithelial regulation of airway reactivity to MCh in vitro, and airway epithelial ion transport. Male rats were exposed by whole body inhalation for 6 h to air or aerosolized MWCNT (0.5, 1 or 5 mg/m3) for one or nine days. Eighteen h after 1 d exposure to 5 mg/m3 MWCNT, basal RL was increased and basal Cdyn was decreased; changes did not persist for 7 d. Reactivity to MCh (RL) was increased and Cdyn responses were decreased at 18 h, but not 7 d after exposure to 1 and 5 mg/m3 MWCNT. The effects of i.t.-instilled MWCNT and nitrogen-doped MWCNT (N-MWCNT) on pulmonary function and reactivity to MCh at doses comparable to deposition after inhalation of 5 mg/m3 at 1 d and 0.5, 1, and 5 mg/m3 MWCNT 9 d-exposures were compared. Both nanoparticles increased airway reactivity (RL); N-MWCNT did not affect Cdyn responses. Lung function and airway reactivity are altered following a single MWCNT inhalation and generally subside over time. Given i.t., MWCNT's and N-MWCNT's effects were comparable, but N-MWCNT evoke smaller changes in Cdyn responses.