Three varieties of cotton, DPL61, GSA71, and SJ5, were each grown during crop year 1983 in three different locations in the United States, the California San Joaquin Valley, the Texas High Plains, and the Mississippi Delta. After processing, the Cottons were carded, and the airborne dust was exhausted to an exposure room which was remote to the card. Human volunteers were exposed to the carded cotton dusts, and vertical elutriated dust samples were analyzed for dust weight and gram-negative bacterial endotoxin content. The geographic area in which the cottons were grown had a marked effect on the endotoxin contamination of the carded dust in that carding of Mississippi-grown cottons resulted in the most contaminated airborne dusts. Variety effects were noted also. Dusts from carded SJ5 cotton contained the highest concentration of endotoxins, regardless of the geographic source of production. Decreases in acute pulmonary function changes paralleled increases in endotoxin concentrations. These data from cotton study MQ-148 extend and corroborate the findings of the first area of growth/varieties study, MQ-119.