This study was based on a sample of 1,831 farmers with no symptoms of the lower respiratory tract, which was taken from a larger survey population of 12,056 farmers. Forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were determined cross-sectionally in connection with health examinations at local health centres. Background data, which included age, sex, height, presence of atopic symptoms, and smoking habits, were gathered in a postal survey conducted by the Social Insurance Institution of Finland. Mean FEV1 and mean FVC were adjusted for age, sex, and height; FEV1 was also adjusted for FVC. Although atopy (defined on the basis of past or present atopic dermatitis, including infantile eczema, and/or hay fever or other allergic rhinitis) had no effect on mean FEV1, mean FVC was lower in atopic than in non-atopic subjects. Both mean FEV1 and mean FVC were lower in smokers than in non-smokers. Smoking thus influenced both FEV1 and FVC, but affected FEV1 slightly more. The effects of atopy and smoking on FVC seemed to be additive. These results, which imply that atopy may predispose obstruction of small airways, match our previous finding that atopy and smoking increase the occurrence of chronic bronchitis additively.