True resistant hypertension must be distinguished from apparent resistant hypertension, of which important causes include medication nonadherence, illicit drug use, and alcoholism. Ambulatory blood pressure monitoring should be considered to rule out white coat hypertension. The pathogenesis is multifactorial, but the 2 pivotal factors include volume excess and the myriad effects of aldosterone. Aldosterone increases vascular tone because of endothelial dysfunction and enhances the pressor response to catecholamines. It also plays a crucial role in vascular remodeling of small and large arteries. Aldosterone also promotes collagen synthesis, which leads to increased arterial stiffness and elevation of blood pressure. Because aldosterone has been demonstrated to modulate baroreflex resetting, in cases of severe hypertension, there would be fewer compensatory mechanisms available to offset the blood pressure elevation.