The development of structural changes in the systemic vasculature is the end result of established hypertension. In essential hypertension, small artery smooth muscle cells are restructured around a smaller lumen, and there is no net growth of the vascular wall, whereas in some secondary forms of hypertension and in non-insulin-dependent diabetes mellitus, a hypertrophic remodeling may be detected. Indices of small resistance artery structure, such as the tunica media to internal lumen ratio, may have a strong prognostic significance in hypertensive patients. Various antihypertensive drugs seem to have different effects on vascular structure. A complete normalization of small resistance artery structure was demonstrated in hypertensive patients, after prolonged and effective therapy with angiotensin-converting enzyme inhibitors, angiotensin II-receptor blockers, and calcium antagonists. Few data are available in diabetic hypertensive patients; however, blockade of the renin-angiotensin system seems to be effective in this regard.