Estrogen has both rapid vasodilatory effects and longer-term effects on the vasculature. The longer-term effects of estrogen are produced, at least in part, by changes in vascular cell gene and protein expression that are mediated by the ligand-activated transcription factors, estrogen receptor (ER)-α and ER-β. The rapid vasodilatory effects of estrogen do not require changes in gene expression and are produced by estrogen-stimulated increases in endothelial cell nitric oxide synthase activity. This results in nitric oxide-mediated increases in cyclic guanosine monophosphate in vascular smooth muscle cells, which mediate vasodilatation. This article briefly reviews recent progress in this field of vascular biology.