Objective: Heparanase plays a central role in processes of placentation. Abnormal placentation may result in inadequate uteroplacental blood flow, leading to unsuccessful pregnancy outcome and preeclampsia. We aimed to evaluate heparanase expression in placentas of preeclamptic patients. Materials and methods: Placental tissue samples were collected immediately after delivery from 9 preeclamptic patients and 3 healthy controls at term, and were analyzed by immunohistochemistry, western blot analysis and real-time PCR, with regard to the presence of heparanase. Results: Immunohistochemistry staining for heparanase did not differ between normal and preeclamptic placental sections. On the other hand, western blot analysis revealed increased expression of heparanase in preeclpamptic placentas compared to controls, p = 0.001. Similarly, RT-PCR analysis showed also an increased expression of heparanase m-RNA compared to health controls, p = 0.005. Conclusion: Heparanase is over expressed in preeclamptic placentas compared to normal healthy controls, suggesting its role in the development of preeclampsia.