—The purpose of these studies was first to determine if vascular endothelial growth factor (VEGF), a vascular permeability agent, is increased in the serum of women with preclinical and clinical preclampsia (PE), and second to determine how these levels change after delivery. Twenty preeclamptic and 25 normotensive women at term consented to have blood taken pre- and post-delivery. Ten preeclamptic, 10 gestational hypertensive, and 28 normotensive women had blood collected respectively at 12, 20, and 30 weeks gestation and predelivery. Serum was extracted from all samples, and VEGF concentrations were determined by radioimmunoassay. Predelivery, the median serum VEGF concentration in the preeclamptic group was 51.7 ng/mL, and in the control group the concentration was 13.9 ng/mL (P<0.0001). Serum VEGF concentrations fell within 24 hours of delivery in both groups, which resulted in median values of 3.8 ng/mL and 3.2 ng/mL respectively (P<0.3). At 12 and 20 weeks, there was no significant difference between the serum VEGF concentrations in the 3 groups (P<0.3, 0.052 respectively). At 30 weeks, prior to the onset of clinical PE, the serum VEGF levels in the eventual preeclamptic group were elevated significantly compared with the gestational hypertensive and normotensive groups (P<0.001). Predelivery serum VEGF concentrations were significantly elevated in the preeclamptic group and were similar to those in the first study (P<0.0001). These findings suggest that VEGF may be important in the pathophysiology of PE and has the potential to act as a preclinical marker for the condition.