Succinic dehydrogenase and cytochrome oxidase activities were found to be scattered throughout the cytoplasm of ciliated and nonciliated respiratory epithelial cells while ATPase activity was restricted to cilia and areas under the cilia in the regions of the ciliary basal bodies. In order to elucidate the role of ATPase further, tissue cultures of rabbit tracheal epithelium with beating cilia were incubated in a medium perfused with cigarette smoke which resulted in cessation of ciliary motility. Epithelium with beating cilia was positive for ATPase while the epithelium with nonbeating cilia was negative or only weakly positive in a few small scattered areas. The presence of ATPase in beating cilia and its absence in nonbeating cilia agree with biochemical and physiological studies suggesting an association between ATP and ciliary activity.