The effects of carbuterol, orciprenaline, salbutamol, terbutaline and fenoterol tablets at 2 dosages were studied in humans using FEV1 [forced expiratory vol in 1s] and specific airway conductnace as parameters. A placebo was used as a reference. Carbuterol and fenoterol were more potent than the other sympathomimetic competitors. Fenoterol 5 mg was on the average somewhat less potent than 3 mg carbuterol. This difference was not statistically significant for FEV1; it was significant 3 h after intake for airway conductance. None of the drugs produced significant changes of the blood pressure. Carbuterol and 12 mg fenoterol caused a statistically significant increase in heart rate. ECG changes were observed in 8 patients with the different .beta.-sympathomimetics, with the exception of 5 mg fenoterol.