The inflammation in byssinosis is believed to be caused by components in the respirable fraction on cotton mill dust; either directly or by indirect activation of proteins on the surface of the bronchial tree. This study shows an association between lower normal alpha 1 antitrypsin (<=35 µmol/1) in serum and atopy, to the prevalence of byssinosis. These variables are the only ones significantly associated with byssinosis when tested in a logistic regression model, controlling for confounding by dust exposure, smoking and age.