The object of this study was to Investigate the beta-adrenergic receptor binding affinity of 4-acylaminophenoxypropanolamine (10-15) and 5-acylaminonaphthyloxypropanolamine (21-24) derivatives, which were prepared from 4-aminophenol (5) and 5-amino-1-naphthol (16), respectively. The in vitro beta(1)- and beta(2)-adrenergic receptor binding affinities of the newly synthesized compounds were assessed in turkey erythrocyte membrane (beta(1)) and lung homogenates of rats (beta(2)). The binding affinities were compared with that of propranolol (3) (propranolol hydrochloride, CAS 318-98-9). The compound N-[5-(3-tert-butylamino-2-hydroxy-propoxy)-naphthalen-1-yl]- acetamide (22) has beta-adrenergic receptor affinity comparable with that of propranolol and shows selectivity to beta(1)-adrenergic receptors