OBJECTIVE: To examine histopathologic changes and correlation between TNF-α and pSTAT3 expression levels by western blot and immunohistochemical methods in preeclamptic placentas. STUDY DESIGN: Obstetrical properties and biochemical and hematological features of patients with preeclampsia and healthy subjects were compared. Paraffin sections obtained from placenta were stained with hematoxylin-eosin for histopathologic examination. RESULTS: In histopathologic examination of preeclamptic placentas, cytotrophoblastic cellular proliferation, fibrinoid necrosis, endothelial proliferation, and calcified and hyalinized villous spots were observed. CONCLUSION: In preeclamptic placentas, we observed that trophoblastic invasion may downregulate STAT3 phosphorylation and can correlate with TNF-α elevation. Even though trophoblast invasion may interfere with both vascular and immune systems, TNF-a is not directly involved in the STAT3 signaling pathway in the preeclamptic placenta. © Science Printers and Publishers, Inc.