Previous studies have demonstrated that air in swine confinement buildings contains large amounts of dusts, highly contaminated with microorganisms and bacterial endotoxin. A study was undertaken to investigate the respiratory function of workers before and after the work shift in swine confinement buildings. Questionnaires were mailed to workers on swine farms. Dust levels were measured by personal sampling, and the micro-flora in the dust was determined. Work-related symptoms from the lung were frequent. Several workers who were smokers had forced expiratory volume in 1 second (FEV1) values lower than expected when they started work. Among a group of life-long nonsmoking workers the baseline forced vital capacity and FEV1 were not decreased. Changes in the FEV1 over the working shift were generally not found. It is suggested that exposure to dust in swine confinement buildings may lead to respiratory impairment but further studies on larger population samples and different exposure conditions are required.