Respiratory histories and preshift and postshift spirometry were recorded for 90 cotton felt workers and 54 brick workers. Environmental monitoring included area sampling by vertical elutriator and cyclone and personal sampling for respirable dust by cyclone. The prevalence of mill fever and byssinosis was 31% and 5%, respectively, in the cotton workers. Significant dose-response effects were detected for both elutriator and cyclone dust measurements and change in forced expiratory volume at 1 s over the shift. A dose-response relationship was also found for the brick workers.