An inhibition ELISA test was developed in cotton dust extracts. Three monoclonal antibodies were evaluated for their capacity to detect changes in the amount of Lipid A detected in chemically-treated cotton dusts. Lipid A and LPS from cotton dust were extracted in boiling water for 1 or 2 hr or in boiling 0.1% SDS for 1 hr. The latter enhanced the amounts of Lipid A accessible for detection by the antibodies. Two antibodies were able to rank the relative toxin (Lipid A) content of chemically treated dusts in the same order of toxicity as shown by guinea pigs in the cotton dust acute toxicity model. The need for improved methods for extraction of Lipid A and LPS from cotton dust are described in the context of these results