To investigate the relationship between the emphysematous changes and bronchodilator responses in patients with chronic airflow obstruction (CAO), we studied the correlation between bronchodilator response to 10 mg inhaled metaproterenol and the extent of emphysema, using selective alveolobronchogram (SAB). Fifty-one patients with CAO were classified into 3 groups by the extent of emphysematous changes detected by SAB. In group 1, no or mild emphysematous change was observed on SAB (n = 9); in group 2, there were significant emphysematous changes but the involved area was less than 75% (n = 17); in group 3, emphysematous change was extensive and covered more than 75% (n = 25). The post-bronchodilator forced expiratory volume in 1 sec (FEV1) of patients in group 3 was significantly lower than in groups 1 and 2. The mean value of changes of FEV1 as a percentage of predicted FEV1 of patients in group 3 was significantly lower than in groups 1 and 2. These results indicated that the extent of emphysematous change correlated positively with the severity of fixed airflow obstruction, and negatively with the bronchodilator response.