Effects of aging and glucocorticoid therapy on bronchoalveolar lavage (BAL) cells, particularly lymphocytes, neutrophils and eosinophils, were examined in 81 patients with asthma. 1. The proportion of BAL lymphocytes tended to increase with aging in asthmatics under age 69 years, and the proportion was significantly higher in patients with asthma between the ages of 60 and 69 than in those under age 39 and between the ages of 40 and 49. 2. The proportions of BAL neutrophils and eosinophils were not related to aging. 3. The proportion of BAL lymphocytes was higher in patients without glucocorticoid therapy than in those with steroid-dependent intractable asthma (SOIA) in those under age 69 years. In patients between the ages of 50 and 59, the proportion of BAL lymphocytes was significantly higher in patients without glucocorticoids than in those with SOIA. 4. The proportion of BAL neutrophils was higher in patients without glucocorticoid therapy than in those with SOIA, and the difference was significant in patients between the ages of 60 and 69. 5. The proportion of BAL eosinophils was not related to glucocorticoid therapy. These results suggest that the proportion of BAL lymphocytes and neutrophils is affected by aging and glucocorticoid therapy, but not BAL eosinophils.