A correlation between the proportion of eosinophils in bronochoalveolar lavage (BAL) fluid and amount of expectoration was examined in patients with atopic asthma. The subjects were divided into two groups : cases with high proportion (20% of more) (group A) and low proportion (less than 5%) (group B) of eosinophils in the BAL fluid. Any significant difference was not paesent in the value of each ventilatory parameter between the two groups. The amount of expectoration/day was significantly higher in group A compared with group B (p<0.001). These results suggest that eosinophilia in BAL fluid correlates to mucus hypersecretion in the airways of patients with atopic asthma.