Subjects of both genders in investigation for resistant systemic arterial hypertension at the Hypertension Unit, whose arterial pressure control was not achieved by primary care assistance despite regular use of three anti-hypertensive drugs, including one diuretic. All subjects received standard drug therapy, aiming at achieving outpatients clinics pressure <140/90mmHg and were re-evaluated up to four weeks later, including 24h ambulatory arterial pressure monitoring.