Antigen-induced bronchospasm is associated with an impairment of airway mucociliary clearance, but the duration of this defect has not been examined. In the present study, we determined the time course of mucociliary dysfunction following inhalation challenge with Ascaris suum extract in conscious sheep with hypersensitivity to this antigen. Tracheal mucous velocity (TMV) as an index of mucociliary function, pulmonary resistance (RL), and arterial oxygen tension (Pao2) were measured prior to, immediately after, and serially for 8 h after inhalation challenge. TMV and Pao2 were then measured periodically for at least 2 wk. Immediately after A. suum challenge, mean RL increased to 264% of base line (P less than 0.05), and mean Pao2 decreased to 61% of base line (P less than 0.05). By 2 h postchallenge, mean RL and Pao2 had returned to base line but mean TMV had fallen to 61% of base line (P less than 0.05). Mean TMV reached a minimum of 35% of base line after 5 h (P less than 0.05) and remained significantly depressed between 37% and 54% of base line for 7 days; by day 9, mean TMV had returned to base line. Inhalation challenge with a control antigen (ragweed) failed to alter mean TMV, RL, and Pao2 during the first 8 h and TMV and Pao2 at any time throughout the 2-wk observation period.(ABSTRACT TRUNCATED AT 250 WORDS)