Naive subjects were exposed to cotton dust in a model cardroom. Spirometry, procoagulant activity of blood monocytes with and without in vitro incubation with endotoxin and -thromboglobulin in blood were determined before and after cotton dust exposure. There was a significant correlation between endotoxin induced PCA from blood monocytes, taken before exposure and the decrease in FEV(1) after cotton dust exposure. The results suggest that cell reactivity may be involved in functional changes seen after cotton dust exposure.