This study examined the relationship of cigarette smoking and endothelial function in pregnant women by comparing smokers with nonsmokers. Endothelial function was assessed at 28-32 weeks of gestation by flow-mediated dilatation (FMD) using ultrasound of the brachial artery. The initial FMD was significantly different between the smoking group (n = 21) at 4.0 +/- 2.3, indicating endothelial dysfunction, and the nonsmoking group (n = 20) at 9.7 +/- 4.0 (P < 0.001). After smoking, this difference in the groups persisted. Babies who were growth restricted (<10th percentile) had mothers with a significantly lower FMD, that is endothelial dysfunction. This work demonstrates persistent endothelial dysfunction in smoking pregnant women.