In preliminary studies of antigen-induced airway inflammation, we noted an apparent increase in peribronchiolar mast cell number. Experiments were thus undertaken to investigate the nature of this migration of mast cells into the central and peripheral airway epithelium and to determine its time course. The tracheae and small airways of 10 anesthetized mongrel dogs were exposed via a bronchoscope to Ascaris suum antigen (Ag), fMet-Leu-Phe (fMLP), ovalbumin (OVA), and isotonic saline (SAL). In the central airways, all stimuli provoked a significant increase (P less than 0.05) in mast cell numbers at the base of the airway epithelium within 3 h. In the peripheral airways, only Ag aerosol stimulated a significant mast cell increase compared with unexposed tissue. In a second series of experiments, the trachea of seven dogs were exposed to 0.026, 0.26, and 2.6 micrograms of Ag. The tissue was collected at 1, 3, 6, and 10 h after exposure. In these experiments, there was a significant mast cell increase seen within 1 h but it was not dose dependent. By 6-10 h after exposure, mast cell counts were not significantly different from the unexposed condition, which is consistent with the idea that some of the cells either degranulated or migrated into the airway lumen. We conclude that mast cell migration is an acute response that can be demonstrated within 1 h of stimulation with Ag. The observation that nonimmunological stimuli may, in some cases, also stimulate mast cell movement affords the possibility that this process represents a generalized response to airway irritation.