Neurokinin (NK) B has been recently demonstrated to be secreted by the placenta in preeclampsia suggesting it may modulate pathophysiological events of the disease. The aim of this study was to investigate whether NKB is the circulating factor associated with preeclampsia or not. In 22 preeclamptic and normotensive pregnant women, the peripheral and umbilical cord blood NKB levels were measured by radioimmunoassay. The NKB levels in women with preeclampsia were 0.70 (0.53–0.92) nmol/L in peripheral blood and 1.92 (1.42–2.35) nmol/L in umbilical cord blood. In normotensive pregnant women, NKB levels were 0.43 (0.29–0.61) nmol/L and 0.14 (0.07–0.33), respectively. Significantly higher levels of NKB were measured in preeclamptic women compared with normotensive pregnant women in umbilical cord blood. These results suggest that NKB enters both fetal and maternal circulation and may modulate fetoplacental hemodynamics.