We have previously reported that aqueous extracts of bulk cotton can stimulate alveolar macrophages to secrete interleukin 1 (IL-1), a monokine that is an important mediator of acute inflammation. The amount of IL 1 produced when macrophages were exposed to the bulk cotton extracts correlated with the endotoxin content of the extracts. We have extended these observations by comparing the endotoxin content of the bulk cotton extracts with the airborne endotoxin levels observed when the samples were carded and with the acute pulmonary response of human subjects exposed to the dust.