There is much evidence that people who had low birthweight tend to have higher blood pressure in later life. However, the mechanisms that mediate this relation are unknown. We argue that, in fetuses whose growth is impaired, synthesis of elastin in the walls of the aorta and large arteries may be deficient, and that this deficiency would lead to permanent changes in the mechanical properties of these vessels. Over a lifetime, such changes could predispose an individual to higher blood pressure, increased left-ventricular mass, and cardiovascular disease.