Changes in pulmonary function following bronchochallenge by potential byssinogenic agents and mediators were studied in rabbits. Female New-Zealand-white-rabbits were challenged bronchial with 0.1 milligram per milliliter (mg/ml) cotton dust extract, 0.1mg/ml cotton bract extract, 1mg/ml endotoxin, 1mg/ml n-formyl-methionyl peptide (FM), 10mg/ml 5-hydroxytryptamine (50679) (5HT) or 1mg/ml prostaglandin-F2-alpha (PGF). Methacholine (55925) at 10mg/ml was used as a positive control agent and saline as a negative control. Pulmonary function parameters, such as respiratory flow, resistance, tidal volume, and compliance were determined at 5 minute intervals up to 60 minutes post challenge. Resistance was used as the most accurate measure of bronchoconstriction. Animals were classified as: mild responders, increases in resistance of 125 to 149 percent over baseline; moderate responders, increases of 150 to 199 percent; or severe responders, increases in resistance of 200 plus percent over the baseline value. FM caused the most consistent severe response, with four out of five animals showing this response. The cotton bract and dust extracts produced increased resistance in four out of five and three out of five rabbits, respectively. Only one of five rabbits responded to endotoxin, showing a moderate response. 5HT produced a response in three out of five and PGF a response in two out of five rabbits. All animals responded to methacholine; the reaction was immediate and severe. Saline challenge caused no significant increase in resistance over a 60 minute period. The authors conclude that the rabbit can be used successfully for quantitatively measuring various pulmonary function parameters following bronchoprovocation.