Results: apoptosis in all stages of trophoblast differentiation, number of syncytial knots per individual villus and the total number of syncytial knots were significantly higher in preeclamptic placentas than in control group placentas. Fas ligand expression was significantly less, and Bcl-2 expression significantly greater in the villus trophoblast among the study subjects compared with controls. There was no difference in the trophoblast proliferation between groups. Conclusion: our findings might suggests that increased apoptosis and syncytial knots formation combined with reduced Fas ligand expression could be involved in pathophysiological mechanisms of preeclampsia.