Objective: to test whether an abnormal increase in circulating free fetal DNA concentration in maternal plasma can be detected in preeclampsia before the onset of the clinical disease and so, whether it can be used as a predictor marker for preeclampsia. Setting: Benha University Design: prospective clinical trial Materials and Methods: Blood samples were collected early in pregnancy from singleton pregnant women. Sixteen women subsequently developed preeclampsia as the only ante natal complication. Another 36 subjects of those who are carrying male fetuses, and have no antenatal complications were selected as positive controls. Samples from 9 pregnant women carrying female fetuses and have no antenatal complications were selected as the negative controls. DNA was extracted from the plasma and the amplified DNA was analyzed by electrophoresis. Results: there was a statistically highly significant increase in the double stranded DNA concentrations in preeclamptic patients as compared to controls (p < 0.001), and this increase is significantly higher in early onset PE than late onset one. There was an increase in circulating free fetal DNA concentrations in PET patients prior to the onset of clinical disease than in those of positive controls with matched gestational ages. Conclusions: free circulating total and fetal DNA in maternal plasma were increased in patients of PE before the onset of it's clinical symptoms and signs as compared to gestational matched control pregnancies. Keywords: fetal DNA, maternal plasma, Pre-eclampsia, PCR