The Th2 cytokines IL-4 and IL-13 are thought to play critical roles in the airway inflammation and hyperresposiveness that characterize asthma. Recent evidence indicates that IL-13 can mediate these effects by acting directly on airway epithelial cells. Here we evaluated early (STAT6 phosphorylation) and delayed (GM-CSF and TGF-2 secretion) responses of airway epithelial cells to IL-4 and IL-13 stimulation, and the dependence of these responses on the culture technique employed. As expected normal human bronchial epithelial cells grown on microporous inserts at an air-liquid interface (ALI) expressed a well-differentiated mucociliary phenotype; in contrast cells grown on plastic in submerged cultures were poorly differentiated. When stimulated with IL-4 or IL-13, the magnitude and duration of STAT6 phosphorylation under the differing culture conditions were statistically indistinguishable. In contrast, cytokine secretion responses to IL-4 and IL-13 were highly dependent on the culture technique; cells cultured on plastic exhibited significant concentration-dependent increases in GM-CSF and TGF-2 secretion, while cells grown at ALI showed no statistically significant response. These results demonstrate that the coupling between early signal transduction responses to IL-4 and IL-13 and downstream functions such as cytokine secretion may be critically dependent on the cell culture technique employed, and the resulting differentiation status of bronchial epithelial cells.