Our goal in this study was to detect endothelial function in normal and preeclamptic patients by using color Doppler sonography and plasma fibronectin levels. The increased ratio of the brachial artery diameter during shear stress, and plasma fibronectin levels were measured in 15 preeclamptic and 11 normal, gestational-age matched pregnant patients. The test was repeated at the postpartum second and sixth weeks in the preeclamptic group. In addition, the plasma fibronectin levels of all patients were measured. The increased ratios were 4.26+/-0.69% vs 12.18+/-1.97% in the preeclamptic and normal patients, respectively ( P=0.003). At the second and sixth postpartum weeks, the ratios were 6.67+/-0.89% and 9.27+/-1.16% in the preeclamptic group, revealing a significant improvement in the sixth week ( P=0.001). Fibronectin levels were 0.80+/-0.11 g/L vs 0.45+/-0.06 g/L in preeclamptic and normal patients ( P=0.01). The correlation coefficient between the fibronectin levels and increase rate was r=-0.38 and P=0.05. We conclude that endothelial dysfunction, which is fundamental to preeclampsia, can be detected by using color Doppler sonography.