Respiratory symptoms, forced vital capacity, and the single breath N2 test were assessed in male employees (25 to 54 yr of age) who had been employed for more than 5 yr in the mining industry in Manitoba. The results were compared with those in a similar group of men selected from the general population. The prevalence of cough and/or phlegm in both nonsmoking and smoking mining employees was significantly greater than that in the sample of the general population (p less than 0.05). In both nonsmokers and ex-smokers amongst the mining employees, the parameters derived from the single breath N2 test tended to be lower and maximal expiratory flow rates tended to be higher than in comparable groups in the general population sample. In smokers, FVC, FEV1, FEV1/FVC, maximal expiratory flow rates, RV/TLC, and the slope of phase III were significantly worse in smelter workers than in underground workers. Alterations in lung function in those who worked underground, but not in those who worked in the smelter, was related to the duration of employment in the industry. The data suggest that exposure to mining irritants may result in disorders of lung function, and that this effect is greater in cigarette smokers.