The chemistry, pharmacokinetics, mechanism of action, clinical studies, adverse effects, toxicology, indications, contraindications, drug interactions, and dosing of minoxidil, a recently approved antihypertensive agent, are reviewed. Minoxidil is an orally effective vasodilator that selectively relaxes peripheral arteriolar smooth muscle, Reflex tachycardia, renin stimulation, and sodium retention occur when minoxidil is used and so it requires the concomitant use of a diuretic and a sympathoplegic agent, usually a beta blocker. Hirsutism and pericardial effusions are additional adverse effects. Minoxidil is indicated in the management of severe hypertension in patients who do not respond to standard antihypertensive agents. In controlled and unctrolled studies, minoxidil was effective in patients with hypertension secondary to renal or renovascular disease and in patients with essential hypertension. Minoxidil is a potent antihypertensive agent with adverse effects that limit its use to patients resistant or intolerant to other drugs.