To evaluate the pathogenetic role of leukotrienes in bronchial asthma, the release of leukotrienes from bronchoalveolar lavage cells stimulated by calcium ionophore A23187 was measured by high performance liquid chromatography. The release of leukotrienes from bronchoalveolar lavage cells in asthmatics with simple bronchoconstriction did not increase compared to those with other types of asthma. The number of BAL eosinophils in asthmatics with bronchoconstriction and hypersecretion increased. The release of leukotriene C4 from BAL cells in asthmatics with type Ib (hypersecrection type) was higher than that in those with type Ia (bronchoconstriction type). The release of leukotriene B4 was also signicantly higher in asthmatics with type Ib than that in those with type II (bronchiolar obstruction type). The number of BAL neutrophils increased in asthmatics with bronchiolar obstruction. However, the release of LTB4 from BAL cells did not increase. In patients with diffuse panbronchiolitis, the number of BAL neutrophils increased and the release of LTB4 from BAL cells was significantly higher than that in asthmatics with bronchiolar obstruction. These results suggest that leukotrienes play a role in the pathogenesis of bronchial asthma with hypersecretion.