Dynamic spirometry with flow-volume curves and measurement of static lung volumes in a body plethysmograph were done in 11 patients with reversible airways obstruction before and up to 240 min after inhalation of 20 mug SCH 1000 and of another 40 mug 60 min later. Forced expiratory volume in 1 s (FEV1), vital capacity (VC) and maximal expiratory flow at 50% VC (V 50% VC) increased successively, reaching maximum after 120 min. In a second part of the study 13 patients inhaled 2+4+8 puffs of SCH 1000 (280 mug in all) at 30-min intervals. PEFR increased significantly up to 224 l/min (44% of predicted normal), with increasing number of SCH 1000 inhalations; no further general effect occurred after additional 3 puffs of terbutaline. Heart rate and blood pressure showed no clinically significant changes. No subjective or objective side-effects were noted.