Serum, plasma and urine were collected pre-exposure and after 4 hours of work from 76 byssinotic and nonbyssinotic cotton mill workers. Workers were grouped as to pulmonary function change, byssinotic history, smoking history and allergy history. No statistical significance was noted in IgG, IgM, IgA, IaE or C4 concentrations between any group of workers. Pre- and post-exposure serum C3 concentrations were statistically different for all workers regardless of category. Cotton dust specific IgE allergin tests demonstrated only 3 workers with significantly elevated values, however, none of these workers were byssinotic. Thromboxane B2 levels were also determined in the plasma and urine.