Objective. The aim of the study was to investigate the role of malondialdehyde, nitric oxide and adrenomedullin in the etiopathogenesis of preeclampsia. Material and Methods. Forty-two pregnant women with preeclampsia and 30 healthy pregnant women were involved. The plasma concentrations of malondialdehyde, nitric oxide, and adrenomedullin were compared between the study group and the control group. Results. In women with preeclampsia the plasma concentrations of malondialdehyde was higher while nitric oxide and adrenomedullin concentrations were lower compared to control subjects. Conclusion. We concluded that the plasma levels of ADM and NO are decreased while MDA levels are increased in subjects with preeclampsia and that might contribute to the pathophysiology of preeclampsia through the lack of a paracrine vasodilatory effect on uteroplacental blood flow.