Characteristics of airway response in steroid-dependent intractable asthma (SDIA) were examined in 86 asthma patients (43 with SDIA and 43 with non-SDIA) divided into three age groups: 20-39, 40-59 and 60+ years, by observing cellular composition of bronchoalveolar lavage (BAL) fluid and ventilatory function. 1. The level of serum cortisol was significantly lower in patients with SDIA than in those with non-SDIA in all age groups. 2. The proportion of lymphocytes in BAL fluid was significantly decreased in patients with SDIA compared to results in non-SDIA patients in the age between 40-59, and over 60+ years, While BAL neutrophils were significantly increased in SDIA patients compared to results in non-SDIA patients in the age group over 60 years. 3. Of ventilatory parameters, the values of % FVC, FEV(1.0%), % MMF and % V(25) were significantly lower in SDIA patients over the age of 60 compared with non-SDIA subjects of the same age group. These results show that in SDIA patients the proportion of BAL lymphocytes decreases and the proportion of BAL neutrophils increases with aging, and that ventilatory function in SDIA patients also decreases with aging compared to non-SDIA patients.