In addition to its contractile properties, airway smooth muscle may contribute to the pathogenesis of asthma by increased proliferation, and by the expression and secretion of pro-inflammatory cytokines and mediators. Studies of airway smooth muscle cells in culture have shown that many mitogenic mediators can induce proliferation, and that these may therefore, contribute to the increase in airway smooth muscle mass observed in asthma. Other mechanisms for airway smooth muscle proliferation include the interaction with inflammatory cells such as T-cells and eosinophils. Airway smooth muscle cells may also be a source of inflammatory mediators and cytokines, in particular chemokines, thus implicating airway smooth muscle cells as contributors to the inflammatory mechanisms of asthma. The pro-activating signals for converting airway smooth muscle cells into a proliferative and secretory cell in asthma are unknown, but may include viruses and immunoglobulin E. Airway smooth muscle contractility may also be altered in response to inflammation. Airway smooth muscle cells may play an important interactive role with inflammatory and other structural cells, contributing to inflammation, injury and repair of the airways. Such a recognition makes it imperative to consider the airway smooth muscle as a target of therapeutic drugs for suppressing not only the contractile but also the proliferative and secretory effects of asthma.