Results from previous studies suggest that symptoms in the byssinosis syndrome are initiated through mediators for inflammation and bronchoconstriction. Potent mediators derived from cell membrane phospholipids are prostaglandin, thromhoxanes, leukotrienes and platelet activating factor. Experiments were undertaker where subjects not previously exposed to cotton dust were exposed at two different occasions in an experimental cardroom for four hours. On one occasion, the subjects were treated with acetylsalicylic acid (ASA). Measurements of lung function, subjective symptoms and blood neutrophils were made before and after the exposure. No difference was found in the FEV(1) decrease over the exposure period. The increase in blood neutrophils after cotton dust exposure was also equal in the two groups.