Twenty thoracic aortas were obtained post-mortem from subjects between the ages of 14 and 90 years who had previously been recorded as normotensive. Full wall thickness samples of 1 cm diameter were taken at six sites between heart valve and diaphragm. Lipid-free dry weight (mg per sample) and amounts (mg per sample) and concentrations (mg/mg dry weight) of collagen and elastin were determined. Lipid-free dry weight and amount of collagen showed highly significant decreases with age (P < 0.0001), with the amount of elastin less so (P = 0.003), representing losses of 92%, 80% and 62%, respectively, between the ages of 14 and 90 years. In contrast, the concentrations of both collagen and elastin increased significantly with age (P < or = 0.0002) by 72% and 140%, respectively, over the age range studied. However, in both cases, the increase occurred substantially after the age of 45. Therefore, besides demonstrating loss of collagen and elastin from the aortic wall with age, these results suggest strongly that there is a parallel loss of other aortic components at a rate which outstrips that of either collagen or elastin in later life.