A study conducted in the rural areas of two counties in east-central Alberta, Canada.To investigate the relationship between lung health and dust exposure in farmers.A cross-sectional study of 781 farmers growing grain crops and raising livestock. Measurements included a questionnaire on respiratory symptoms, smoking habits and occupation, skin prick tests using common aeroallergens, and spirometry.Immediate skin reactivity to common aeroallergens was less prevalent in farmers with higher reported intensity of dust exposure. Respiratory symptoms suggestive of bronchitis had a significant dose-response relationship with the reported intensity of dust exposure. Respiratory symptoms consistent with bronchial responsiveness were significantly positively associated with cumulative dust exposure. There was a significant positive association between a physician's diagnosis of bronchitis and intensity of dust exposure. FEV1 and FEV1/FVC were significantly negatively associated with cumulative dust exposure. Ten years of exposure to a moderate dust level was associated with a deficit of 43 ml in the FEV1 and a deficit of 0.44% in the FEV1/FVC.Despite evidence of worker selection related to dust exposure, these farmers experienced respiratory symptoms, respiratory conditions, and reduced lung function associated with reported occupational dust exposure.