The aim of this study was to evaluate if treatment with inhaled formoterol is appreciated by asthmatics and whether it causes tachyphylaxis. Twenty stable asthmatics were included in a randomized, double-blind, crossover study. They were treated for two weeks either with formoterol or salbutamol, with one week washout inbetween. They were given 12 micrograms formoterol or 200 micrograms salbutamol twice daily and instructed to use additional spray doses on demand. On a diary card they recorded the number of doses, asthma symptoms and peak expiratory flow rate (PEFR) before every dose. Forced expiratory volume in one second (FEV1) dose-response curves for salbutamol (total dose 1.3 mg) were performed before and after each treatment period to evaluate development of tachyphylaxis. There was a significant difference in favour of formoterol concerning symptoms, PEFR recordings, spray consumption, and preference. Fifteen patients preferred formoterol and two salbutamol. The dose-response curves before formoterol and before, as well as after salbutamol were almost identical. After formoterol the curve had changed; both basal and maximum values were higher than before. Thus, no evidence of tachyphylaxis was found, compared to the ordinary beta-stimulant treatment.