A survey of 300 grain elevator workers revealed that 77 per cent complained of eye symptoms; 64 per cent, of nasal symptoms; and 88 per cent, of one or more respiratory symptoms on exposure to airborne grain dust. Symptoms on exposure were independent of age and length of employment. Cough and wheezing on exposure were more common among smokers than nonsmokers (P less than 0.025). Nineteen per cent of the workers had had episodes of grain fever. The prevalence of chronic bronchitis was 37 per cent (42 per cent of smokers and 30 per cent of nonsmokers). Wheezes on auscultation were found in 23 per cent. Measurements of lung ventilatory function, as well as diffusing capacity, correlated significantly with age and smoking habits, but not with length of employment. Thirty-seven per cent of the workers had an abnormal mean forced expiratory flow during the middle half of the forced vital capacity (47 per cent of smokers and 13 per cent of nonsmokers), and 34 per cent had an abnormal maximal expiratory flow after exhalation of 50 per cent of the forced vital capacity (40 per cent of smokers and 13 per cent of nonsmokers), whereas only 13 per cent had an abnormal ratio of 1-sec forced expiratory volume to forced vital capacity. There was no correlation between precipitins to fungi, bacteria, grain, or grain dust antigens and acute or chronic respiratory symptoms, lung function, or grain fever. There was, however, a significant correlation between cutaneous reactivity to grain dust and wheezing on exposure (P less than 0.02). Abnormal flows at low lung volumes were more common among cutaneous reactors to common allergens. We concluded that exposure to airborne grain dust can cause acute inflammatory reaction to the exposed mucosa, and it is highly probable that grain dust contributes and, in some cases, causes chronic airway disease.