Low birthweight may predispose to the development of atherosclerosis later in life. We have tested the hypothesis that low birthweight as a result of preterm birth is associated with reduced flow-mediated endothelial-dependent vasodilation (FMD), which is an early stage in the development of atherosclerosis. Mean FMD in adolescents born preterm who had a low birthweight did not differ from that for controls born at term (0.225 mm vs 0.220 mm, SD 0.1 for both means, p=0.78). Our findings indicate that low birthweight attributable to prematurity does not increase the risk of vascular disease later in life.