A cross-sectional study of work-related symptoms and cotton dust exposure was made in 404 man-made fiber and 1,048 cotton operatives in Lancashire spinning mills; 39 cotton-exposed operatives (3.7%) had symptoms of byssinosis. This was associated on regression analysis with cumulative lifetime cotton dust exposure (p < 0.001), total years spent carding (p < 0.001), and currently working in the carding area (p = 0.0041). Smoking habit did not differ significantly between byssinotic and nonbyssinotic workers. Other work-related symptoms were common: chronic bronchitis (CB) and persistent cough. The prevalence of CB correlated positively with dust exposure (r = 0.59). Cotton dust sampling was performed in the work area (SDPRES) and personal breathing zone (PD1). A retrospective estimate of lifetime cotton dust exposure based on SDPRES correlated best with the prevalence of byssinosis (r = 0.797), although correlations with PD1 (r = 0.709) and SDPRES (r = 0.594) were also significant.