We studied the pharmacologic properties of a water soluble extract of wool dust (WDE) using isolated guinea pig trachea. Dose response relationships between WDE and contractions of guinea pig tracheal smooth muscle were established. The effects of pre-treatment with mediator blockers (pyrilamine, atropine) arachidonic acid metabolite inhibitors (indomethacin, BW755C, LY 171883) , and calcium channel blockers (verapamil) and an intracellular calcium antagonist (TMB8) were examined and compared to results with similar experiments using cotton bract extacts. Minimal or no inhibition of contraction were seen with mediator blockers while the effects of arachidonic acid inhibitors were mixed. Both calcium blockers effectively blocked the effects of WDE. In this system WDE does not appear to cause constriction via classic mediator receptors but possibly by influencing arachidonic acid or other cellular metabolic pathways.