The smoking habits of 18 patients with extrinsic allergic alveolitis, 22 with cryptogenic fibrosing alveolitis, and 75 patients with sarcoidosis were compared with the smoking habits of the normal population of the Prairie Region for 1973. The patients were diagnosed at the same two hospitals over the four-year period November 1971--75 and were of comparable age. Non-smoking was significantly associated with allergic alveolitis in men and the three cases in women were all non-smokers. For the other two diseases, smoking habits were similar to those of the local population.