Cyclooxygenase and lipoxygenase metabolites of arachidonic acid are potent modulators of smooth muscle contraction, secretion, cell movement, and a variety of other cellular activities. It is postulated that release of these metabolites could account for the physiological and pathological changes observed in humans and animals following inhalation of cotton dust. Guinea pig lung lavage cells were stimulated with chemically modified cotton dusts. It was found that production of five of the six arachidonic acid metabolites measured were decreased by all but one of the dusts tested. Extraction of cotton dust with DMSO was the most effective treatment in reducing the release of these bioactive compounds by the cells of the lung. Furthermore, there was a high correlation between the production of arachidonic acid metabolites by these pulmonary cells and the concentration of endotoxin in the dust samples.