Evidence exists that the bronchoconstriction measured in guinea pigs inhaling cotton dust extract is mediated by the release of arachidonic acid metabolites. To determine the relevance of this to man, the effect of various pharmacological agents upon the response (sGaw) of the airways to an inhaled extract of cotton dust has been measured in a small group of healthy volunteers using whole body plethysmography. The results using aspirin, indomethacin, terfenadine, cromoglycate, verapamil and FPL-55712 generally support the theory that the constrictor response of the human airways to cotton dust extract is calcium-dependent and not via the release of Prostaglandins. However, preliminary evidence in one subject suggests that leukotriene release is implicated. Work is in progress to investigate these theories further.