The effects of Bromhexin-Metabolite VIII (NA 872) and a new β2-mimetic (NAB 365) on mucociliary function were studied in isolated preparations of the airways of rats, hamsters and cats. NAB 365 markedly increased ciliary activity and was a potent secretolytic agent. Similarly, NA 872 increased ciliary ac- tivity, however, to a lesser degree than NAB 365. Both drugs had opposite effects on the consistency of the secretions. The ability to generate threads increased under the influence of NAB 365 and decreased under the influence of NA 872. It is suggested that the combined usage of these drugs could produce optimal tracheobronchial clearance