Sulfinalol is a hydroxyphenylalkanolamine derivative patented by Sterling Drug Inc. as the antiarrhythmic, antihypertensive, vasodilating, and adrenergic agent. Oral administration of sulfinalol reduces the pressure of conscious spontaneously hypertensive rats. Antihypertensive action of sulfinalol was inhibited by propranolol pretreatment. Sulfinalol demonstrates effective beta-adrenergic blockade at the antihypertensive dose tested as judged by inhibition of the chronotropic responses to sympathetic stimulation and isoproterenol in pithed rats. In the renal hypertensive dog. sulfinalol lowered both systolic and diastolic blood pressure to normal values with an only slight change in heart rate.