A total of 103 samples of sputum from 20 patients with bronchial asthma were examined for appearance of basophils and eosinophils. The results are as follows: 1) Basophilic leucocytes were found in the sputum of patients with bronchial asthma. 2) Basophils appeared in sputum during asthma attacks and disappeared during nonattack stages. 3) The number of basophils in sputum tended to increase at the end of attack stages. 4) High incidence of basophils in sputum was observed in asthmatic patients with low serum IgE levels. 5) Appearance of basophils in sputum was accompanied with that of eosinophils. 6) Appearance of basophils in sputum was related to the number of peripheral basophils, but not to the daily volume of sputum. These results suggest that basophils migrate from the blood stream into bronchial tissues and appear in sputum during attack stages of bronchial asthma.