erythro-5-[1-Hydroxy-2-(isopropylamino)butyl]-7-hydroxycarbostyril (4), which is a terbutaline-type derivative of the bronchodilator procaterol, was synthesized by transfer of the 8-hydroxyl group of procaterol to the 7 position. Compound 4 showed less potent beta-adrenoceptor stimulant activities than procaterol or terbutaline in an in vitro test using guinea pig tracheal muscle and right atrium. In an in vivo assay on anesthetized dogs, compound 4 showed 42 times less bronchodilator activity and 87 times less effect on the heart rate than l-isoproterenol.