BACKGROUND: Preeclampsia (PE) is a systemic pregnancy-related disorder characterized by hypertension, proteinuria, and edema. Free radicals seem to play an important role in the induction of endothelial dysfunction in PE. AIM: The aim of the present study was to investigate serum levels of nitric oxide (NO), peroxynitrite (ONOO-), paraoxonase (PON-1), malondialdehyde (MDA), and lipid profile in preeclamptic patients compared to the women with normal pregnancy. MATERIALS AND METHODS: A total of 68 pregnant women were recruited. They were divided into two groups - Group A, 40 women were a newly diagnosed with PE and Group B, 28 women with normal pregnancy. Anthropometric measurements including body mass index and blood pressure in accordance with biochemical measurements including NO, ONOO-, PON-1, MDA, and lipid profile were done for preeclamptic pregnant women compared to the controls. RESULTS: Pregnant women with pre-eclampsia illustrated insignificant differences in the age (31.22 +/- 2.87) compared to the age of control P > 0.05. There were significant changes in the body mass index (BMI), type of delivery and smoking status of pregnant women with pre-eclampsia compared to the control P < 0.05. Both systolic and diastolic blood pressures were high in pregnant women with pre-eclampsia compared to the control P < 0.01. PON-1 and NO serum levels were significantly decreased (P < 0.01) while ONOO-and MDA serum levels were significantly increased in PE compared to the women with normal pregnancy. CONCLUSIONS: This study concluded that PE is associated with the augmentation of oxidative stress and reduction of endogenous antioxidant capacity regarding PON-1.