This study was conducted to investigate the prevalence of respiratory problems, in particular byssinosis, and to explore factors associated with their occurrence among a group of 595 randomly selected workers representing 40.5% of those exposed to dusty operations in a typical Ethiopian cotton textile mill. A standard questionnaire on respiration was administered and pre and postshift forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were determined for each worker; workers found to have byssinosis and other respiratory diseases were compared with workers having no respiratory diseases in terms of the level and duration of exposure to cotton dust and other variables. Multiple area air samples from different sections were analysed for elutriated cotton dust concentrations (0.86-3.52 mg/m3). The prevalence of byssinosis was 43.2% among blowers and 37.5% in carders in comparison with four to 24% among workers in other sections. Prevalence of chronic bronchitis ranged from 17.6 to 47.7% and bronchial asthma from 8.5 to 20.5% across all sections. Significant across shift decrements in FEV1 and FVC were seen in those workers with respiratory tract diseases compared with those workers without such diseases. A significant dose response relation for pulmonary function and respiratory illnesses was also found by regression analysis. Preventive measures are proposed. Further research including a nationwide survey of textile mills is suggested. This is the first epidemiological study of the textile industry in Ethiopia.