Investigations of asthma cases were made in Kumano-cho, Hiroshima Prefecture, where in almost all homes hair-pencils are manufactured; and the following results were obtained. 1) Among the town population of 4324, people amounting 3528 suffered from some illness and were given any treatment from Jan. to Dec. 1966. Among these patients, 83 cases of bronchial asthma, 19 cases of allergic rhinitis, 7 cases of pulmonary emphysema, 7 cases of chronic bronchitis, 3 cases of bronchiectasis and a case of lung fibrosis were found. 2) Among 80 workers of hair-pencil factories, 20 cases suffered from asthma-like symptoms, and among these 20 cases, 14 were found to be positive in the intradermal reaction using the antigen extracted from the animal hair (sheep, cat, goat, horse, deer, weasel, raccoon dog and flying squirrel etc), material for the hair-pencil. And some of them were found positive in the P-K reaction, too. On the other hand, the patients suffered from bronchial asthma or sea-squirt asthma who lived on another districts, showed fur lower positive intradermal reaction rate than those of the hair-pencil making workers with the same antigen extracts. 3) It is quite certain that, among the asthma cases found in workers manufacturing the hair-pencil, some are caused by the sensitization of the animal hair, material for the hair-pencil.