Vascular structure, function, and mechanics are altered in hypertension, which contributes to an important degree to complications of elevated blood pressure. Vascular hypertrophy with collagen deposition and increased stiffness is found in large arteries, whereas in small arteries, smooth muscle cells are restructured around a smaller lumen, and there is no net growth of the vascular wall, particularly in milder forms of hypertension. Hypertrophic remodeling and increased small artery stiffness may be found in more severe hypertension. Endothelial dysfunction occurs in large or smaller vessels in a variable percentage of patients, particularly in presence of other risk factors such as diabetes, smoking, dyslipidemia, and advanced atherosclerosis. In clinical trials, 1-year treatment with angiotensin-converting enzyme inhibitors, angiotensin AT1receptor antagonists, and long-acting calcium channel blockers corrected small artery structure and endothelial dysfunction in hypertensive patients, whereas &bgr;-adrenergic receptor blockers did not. Improved outcomes in hypertensive patients demonstrated in recent trials with some but not others of these agents could be a consequence, at least in part, of vascular protection offered by some antihypertensive agents.