Thirteen out‐patients suffering from chronic reversible bronchial obstruction were treated on two separate days with two doses of terbutaline aerosol, administered with a 750 ml spacer interposed between the actuator and the mouth, in order to evaluate whether clinical responses showed a dose dependency during a 4‐h period. On each day the two different doses (65 μg versus 250 μg) were inhaled three times at 15‐min intervals. Fifteen minutes after the first dose there was a significant difference in FEV1increase between the small dose and the normal dose, FEV1 being higher after 250 μg, but no significant differences in increase after the 2nd and 3rd inhalations. This study indicates that the bronchodilating effect of terbutaline administered via the spacer is dose‐dependent at the first inhalation, and that succeeding inhalations show no dose‐resp