This study was performed to assess the effects of sulfuric acid inhalation, and partly to examine the potential suitability of the laboratory ferret as a respiratory tract clearance model. Separate groups of ferrets were first exposed nose-only to purified air, 0.5 mg/m3 ofsulfuric acid aerosol, and 1.0 mg/m3 ofsulfuric acid aerosol for 4 h. Following the deposition of radiolabeled tracer microspheres, the clearance rates from the head and chest regions were monitored using collimated radiation detection equipment. The results indicate that (1) neither of the acid atmospheres produced a statistically significant effect on the clearance rate of the head region; (2) the high-acid atmosphere produced a significant acceleration in the clearance rate of the lung region; and (3) the long-term lung clearance rate of the purified air-exposed ferrets was very close to that observed with humans. Also, the ferrets were docile and easy to handle, and seemed to be well suited to this type of study. © 1991 Informa UK Ltd All rights reserved: reproduction in whole or part not permitted.