A cohort of both active and retired older cotton textile workers was examined prospectively over a 6-year period to establish the nature and extent of chronic lung disease. Respiratory symptoms and lung function were studied in these workers and in a group of similarly aged controls. The cotton textile workers had higher prevalence and attack rates of respiratory symptoms than did controls even with smoking habits taken into account. Chronic bronchitis developed in 16% of all cotton textile workers compared to 1% of controls over the follow-up period (p less than 0.001). The cotton workers suffered a larger loss of lung function over 6 years than did controls. Male workers lost 42 mL/yr of forced expiratory volume in 1 second, although male controls lost only 25 mL/yr (p = 0.001). Similar differences were seen in women, and in both men and women who were nonsmokers. Retired cotton textile workers had more symptoms and disability than active workers. We conclude that chronic lung disease is not only irreversible but may progress even after exposure to cotton dust has ended.