Patients with refractory hypertension, defined as uncontrolled office blood pressure despite use of 5 or more antihypertensive agents, including a thiazide diuretic and spironolactone. After withdrawal from other centrally-acting agents if needed, enrolled patients will be randomized to open-label reserpine 0.1 mg daily for 4 weeks. Twenty-four hour ambulatory blood pressure monitoring will be done at baseline, after the initial 4-week treatment period. All other antihypertensive medications will remain unchanged during the 4-week treatment period. The primary endpoint will be change in 24-hr ambulatory systolic blood pressure.