40 outpatients with chronic obstructive airway disease received the parasympatholytic bronchodilator ipratropium bromide (Sch 1000) and the sympathomimetic bronchodilator fenoterol from a metered dose inhaler. After evaluation of the initial values, first Sch 1000 was administered and 20 min. later airway resistance was measured, then fenoterol was given and a measurement was taken again 20 min. later. On the following day the aerosol inhalants were given in the reverse sequence. After the first inhalation 0.08 mg Sch 1000 proved to be an equally strong bronchodilator as 0.4 mg fenoterol and airway resistance was decreased to 52% and 55%, respectively of the initial value (p less than 0.001). The additional inhalation of the other bronchodilator caused a further slight decrease in airway resistance to a minimum of 47%, but was statistically significant (p less than 0.001) only in the case of the fenoterol/Sch 1000 sequence. The importance of bronchiolar tonus in regard to fluctuation of airway resistance and the possibility of a specific additive bronchodilatory effect of adrenergics and vagolytics is discussed.