In this study, the guinea pig animal model, established at the University of Pittsburgh, was used to compare the pulmonary toxicity of DB 1/88 and DB 11/82 cotton dusts. It was shown that the two cotton dusts did not significantly differ microbiologically, had the same endotoxin content and particle size distribution, but had different tannin contents. Concentration response curves, including 95% confidence intervals for both dusts were comparable. These data indicate that the two cotton dusts induce similar pulmonary toxicity.