Epidemiological data suggests lower respiratory infections (LRI) with respiratory syncytial virus (RSV) are capable of causing long-term abnormalities in airway function. To directly test the effects of RSV LRI, we infected adult and weanling BALB/c mice with RSV (A2) or vehicle. Respiratory system impedance was used to assess baseline airway function and responses to iv methacholine (MCh) at 4, 8, 24 and 34 weeks post infection. In vitro airway responses were measured 24 weeks post infection using electrical field stimulation and MCh. Mice infected as adults showed no alterations in airway function. Mice infected as weanlings had increased MCh responses 24 weeks post infection. However, the increased response was not present 34 weeks post infection nor accompanied by alterations in in vitro responses or airway morphometry. This study did not detect long-lasting changes in airway function following RSV infection in mice. These data do not provide support for alterations in airway structure or function being responsible for the observed relationship between RSV infection in infants and asthma in later life. (c) 2006 Elsevier B.V. All rights reserved.