In order to clarify the relationship between agglomerated bronchial epithelial cells, i.e. Creola body (CrB), in the sputum and each pathogenetic factor of bronchial asthma, the incidence of CrB in sputum stained by Papanicolaou's method and observed under a light microscope was evaluated in 45 cases of bronchial asthma and 9 cases of obstructive pulmonary diseases. The following results were obtained: 1) CrB was observed specifically in the sputum of patients with bronchial asthma. In comparison with CrB-negative cases, CrB-positive cases had a greater number of days with attacks and a higher incidence of eosinophils in the sputum. 2) The presence of CrB in the sputum tended to be at a high rate in non-atopic cases with low serum IgE values, but had no obvious correlation with either the incidence of neutrophils in the sputum, the present age of the patient, the severity of the disease or bronchial hyperresponsiveness to methacholine. These results suggest that the involvement of histolesionable factors such as persistent bronchial contraction and release of major basic protein from eosinophils in the airway may lead to the formation of CrB.