Airway inflammation is associated with the acute byssinotic reaction following inhalation of cotton dust or cotton dust extract (CDE) by humans or experimental animals. Endotoxin, tannin and several other compounds are all candidates for inducing the inflammatory response of the airways. We compared polymorphonuclear cell (PMN) influx and chemotactic activity of the bronchoalveolar lavage fluid (BALF) from rabbits acutely exposed to CDE or equivalent dose of tannin. Only a portion of the PMN influx following CDE exposure was reproduced after tannin inhalation. Most of the chemotactic activity found in BALF after CDE exposure was due to high molecular weight compounds (7 kD to 20 kD) while low molecular weight factors (>0.8 kD) were responsible for most for the chemotactic activity after tannin inhalation. Not surprisingly, airway reaction to the complex CDE could not be entirely explained the effects of one single compound, tannin.