Some propanolamine derivatives were synthesized and their β-adrenergic blocking activities were determined. Among the compounds tested, all compounds with benzothiazole nucleus were found to have potent β-adrenergic blocking activity, and those with other nuclei failed to produce substantial β-blocking activity with one exception. Three compounds with benzothiazole nucleus were more potent than sotalol in their β-blocking activity, and the other two were equipotent to sotalol. One with benzotriazole nucleus had about the same β-blocking activity as sotalol.