Characteristics of each asthma type classified by clinical symptoms and findings were studied in 72 patients with bronchial asthma. 1. Ventilatory function tests showed that the values of % MMF, % V(50) and % V(25) were significantly lower in patients with bronchiolar obstruction (type II) compared to the values of those with simple bronchoconstriction type (type Ia) and those with bronchoconstriction + hypersecretion (type Ib). 2. The proportion of neutrophils in bronchoalveolar lavage (BAL) fluid was significantly higher in type II than in type Ia and type Ib. Several patients with type Ib showed higher proportion of BAL eosinophils. 3. The release of LTC(4) from leucocytes was significantly lower in type II compared with type Ia and type Ib. There was no significant difference in the release of histamine and LTB(4) among the three asthma types.