Hoping to get more insight into a role of vascular endothelial growth factor (VEGF), a putative substance involved in the development of preeclampsia, we measured concentrations of soluble VEGF receptor-1 (sVEGFR-1), a natural antagonist of VEGF, in serum from women with (n = 31) and without (n = 52) preeclampsia. The concentrations of sVEGFR-1 in serum from women with preeclampsia (median 7791 pg/mL) were > 6-fold higher than those from control (1132 pg/mL, p < 0.0001). The levels of sVEGFR-1 decreased markedly after delivery in both groups. Serum sVEGFR-1 levels of non-preeclamptic women were positively correlated with gestational age (r = 0.570, p < 0.0001), whereas those of preeclamptic women exhibited no correlation with gestational age (r = -0.130, p = 0.476). These findings may point to an involvement of sVEGFR-1 in the pathophysiology of preeclampsia possibly by antagonizing of VEGF effects on the formation of placental vasculature and maternal endothelial cell function.