Tracheobronchography using tantal powder was used to study the functional activity of the intact and altered bronchial mucosa that manifested itself as the unchanged outline of the mucosa and its clearance (mucociliary clearance). With the intact mucosa, the sequence of its clearance was established; the mechanism of powder transport was studied, which showed up as the appearance of metachronal fields, fusion of particles into conglomerates that form currents that direct towards the larynx. The clearance of the mucosa was over by hours 20-24. With the altered mucosa (tuberculosis and other diseases), the sequence and mechanism of its clearance were impaired. The outline of the mucosa was chaotic; there was a long powder retention (48-72-hour or more) in cancer and bronchoectases. There was retrograde transport of particles into the minor bronchi. The found differences in the activity of the mucosa in pulmonary tuberculosis and lung cancer allow this method to be used for differential diagnosis.