Studies in animal models demonstrate that angiotensin II and its downstream signaling molecules, that is, matrix metalloproteinases and monocyte chemoattractant protein-1, increase within the diffusely thickened intima of central arteries with aging. Whether such age-related changes occur within the human arterial wall is unknown. We harvested “grossly normal thoracic aortas” from 5 young (20±3 years) and 5 old white males (65±6 years) at necropsy, after death from traumatic causes. The intimae of older samples were markedly and diffusely thickened compared with younger intimae and contained increased levels of angiotensin-converting enzyme, angiotensin II, angiotensin II receptor type 1, matrix metalloproteinases 2/9, monocyte chemoattractant protein-1, and collagen I and III proteins. In situ activities of metalloproteinases 2/9 were also significantly enhanced within old, normal aortas. The thickened intima of older aortas also contained a 5-fold increase in the embryonic form of smooth muscle myosin heavy chain–labeled cells than that of younger aortas, and these fetal-type cells were colocalized with angiotensin II protein staining. The ability of isolated smooth muscle cells to invade an artificial basement membrane in response to a monocyte chemoattractant protein-1 gradient increased with age. Furthermore, angiotensin II increased the invasive capacity of young smooth muscle cells, and this effect was reduced by a metalloproteinase inhibitor or an angiotensin II receptor blocker. Thus, in the absence of lipid infiltration, the aged human aortic wall exhibits a proinflammatory profile that renders it a fertile substrate for the development of arterial disease, for example, atherosclerosis and hypertension.