New beta-adrenergic blocking agents, most of which do not contain an aromatic nucleus, were synthesized. They were derived either from alkylamino-aliphatic oxime ethers or alkylamino-aliphatic ethers. Most active among these are O-[3-(tert-butylamino)-2-hydroxypropyl]acetoxime (8; trachea pA2 = 7.65) and 1-isobutoxy-3-(tert-butylamino)-2-propanol (15; trachea pA2 = 7.49), both of which displayed bronchoselectivity (beta 2/beta 1 ratio approximately 15). The role and importance of the aromatic nucleus in this class of compounds are discussed.