In vitro effects of ethanol on human umbilical artery and vein were studied. Ethanol (0.5–2.0%) elicited a dose-dependent contractile response both in the umbilical arterial and venous strips in Krebs’ and Ca2+-free Krebs’ solution. In umbilical artery, but not in vein, ethanol shifted the Ca2+-induced dose-response curves to the right in a parallel manner along with a significant reduction in K+-depolarized maximal tension. These result demonstrate that ethanol can elicit a potent contractile response both in human umbilical arteries and veins and could aid in explaining why ethanol can induce the fetal alcohol syndrome.