A series of procaterol derivatives having a substituent at the 7-position of the carbostyril moiety was synthesized. Halogenation of procaterol and its homologues gave the 7-halogeno derivatives (3). Nitration of the procaterol analogues afforded the 7-nitro derivatives (4), and the catalytic reduction of 4 gave the 7-amino derivatives (5). These compounds showed weak β-adrenoceptor stimulant activities in anesthetized dog.