The ciliated epithelium of the mammalian respiratory tract is involved in tracheobronchial clearance. We propose to refine available optical techniques to quantitate ciliary activity in mammalian respiratory epithelium and to correlate these data with morphological information obtained by transmission and scanning electron microscopy. High-speed cinematography with Nomarski and dark-field optics, as well as high-sensitivity closed-circuit videotape recording, will be used to analyze ciliary beat pattern and metachronal coordination normally, and as a response to pharmacological agents and cations, in several in vitro model systems. These will consist of isolated string of ciliated cells, intact single cells and preparations of demembranated, reactivated isolated cilia, all obtained from mammalian trachea and bronchi. Such model systems will provide information regarding ciliary function free from other physiological responses.