We evaluated lipid peroxidation in serum, placenta and decidua basalis and antioxidant defenses in preeclampsia and normal pregnancy. The study group consisted of 70 women with preeclampsia and 72 healthy pregnant women. Lipid peroxides in serum, placenta and decidua basalis, and serum vitamin E and total carotene were measured by spectrophotometric methods. Unpaired Student's t-test, χ2-test and Pearson correlation test were used for the statistical analyses. Levels of lipid peroxides in serum, placenta and decidua basalis were markedly higher; and serum vitamin E, total carotene, bilirubin, albumin levels were markedly lower in preeclamptic pregnants compared with healthy pregnant women. Our findings demonstrated that both placenta and decidua basalis tissues may be a source of lipid peroxides in preeclamptic pregnancies. Prophylactic antioxidant therapy may abate the disease process. Further studies are needed to clarify the pathophysiology of preeclampsia and effectiveness of prophylactic antioxidant therapy in preeclampsia. © 2002 Elsevier Science Ireland Ltd. All rights reserved.