The results of an intra-individual double-blind study between placebo, orciprenaline and 7-(3-[2-(3,5-dihydroxyphenyl)-2-hydroxy-ethylamino]-propyl)-theophylline (reproterol, Bronchospasmin) were compared in 16 patients with chronic obstructive bronchitis by means of the findings of objective measurements as well as patients' comments. It was shown that the new monosubstance reproterol, a phenylethyl-aminoalkyl-xanthine, is a very potent bronchodilator whose effect persists for at least 6 h. This bronchlysis could be proven on the basis of total and specific airways resistance as having a significantly superior and longer-lasting effect when compared with placebo. Also, when compared with orciprenaline the total broncholytic effect (areas of Raw and SRaw for effect covering time) was significantly better. No essential cardiovascular or subjective side-effects were caused by any of the three preparations inhaled in from of an aerosol equipped with metering valve. Because of its assured broncholytic efficacy and good tolerance, as well as its different forms of application (ampoules, tablets, aerosol, inhalation-solution), reproterol is a recommendable alternative in recent beta2-adrenergic achievements.