Reversible airway obstruction has been shown to be a characteristic finding of early byssinosis. In the chronic phase of this disease, the patterns of respiratory abnormalities have not been well defined. We examined the lung function of a cohort of 383 older (45 yr of age or more), active and retired, cotton textile workers seen both in 1973 and in 1979 in Columbia, South Carolina. A group of control subjects consisted of 277 white community residents of comparable age from Lebanon, Connecticut. Using data at follow-up, 25% of the male and 14% of the female cotton textile workers had moderate to severe obstructive airway abnormalities, as opposed to 13 and 5% for male and female control subjects (p less than 0.01). There were fewer persons with restrictive than with obstructive lung patterns among cotton textile workers and control subjects, but again, abnormalities were more prevalent among cotton textile workers. Overall, 50% of male cotton textile workers and 37% of female cotton textile workers had some abnormality of lung function, as opposed to 29% of male and 20% of female control subjects (p less than 0.001). More abnormalities were present in cotton textile workers than in control subjects when only lifetime nonsmokers were examined. We conclude that there is an increased prevalence of both obstructive and restrictive lung function abnormalities among cotton textile workers when compared with control subjects, with the most common pattern being obstructive.