Axonemal dynein is a high molecular weight Mg2+-ATPase which occurs across the eukaryotic phylogenetic spectrum and interacts with the microtubular doublets of ciliary axonemes to effect ciliary beating. Unlike cytoplasmic dyneins which serve intracellular functions and are relatively ubiquitous in all cells, axonemal dynein is expressed exclusively in mature and nascent ciliated cells. Ciliated cells figure prominently in mucociliary clearance, a primary defense mechanism of the mammalian respiratory airways. Acting in concert with mucus secreting cells, the mucociliary escalator maintains virtual sterility in the airways and lung. Although ciliated cells are the predominant cell type in the airways and serve a critical function in respiratory health, they also are particularly vulnerable to injury. The strategic functional importance of the ciliated cell as well as its susceptibility to injury by infectious agents and irritants has led to development of epithelial cell culture systems which facilitate epithelium-specific studies of injury.