This study reviews the respiratory status of a sample of Vermont male dairy farmers, and a comparison group from industry, matched for age, sex and smoking. Survey instruments included a standardized questionnaire and simple pulmonary function tests. In general, past and present smokers had more respiratory symptoms than never-smokers; and farmers, in all smoking categories, reported symptoms with greater frequency than did their counterparts from industry. Forced vital capacity (FVC) tended to be lower among men with a history of smoking but, within each smoking category, dairymen and factory workers had very similar FVCs. Farmers who had never smoked or who were current cigarette users had lower FEV1/FVC (forced expiratory volume at one second/forced vital capacity) ratios than their controls from industry. Sixteen diarymen demonstrated precipitins to either Micropolyspora faeni (13) or Thermoactinomyces vulgaris, (3), but only one reported a constellation of symptoms compatible with farmer's lung disease. The estimated prevalence of antibodies to thermophilic actinomyces in this farm population was approximately 10 per cent. Although sample sizes were limited, dairymen from small farms tended to be older, have more respiratory symptoms, less satisfactory pulmonary function, and more serologic evidence of exposure to farmer's lung antigens than their counterparts from large farms.