Preeclampsia is characterized by increased lipid peroxidation and diminished antioxidant capacity; however, there is no consensus as to the extent of these conditions. To assess the association of lipid peroxidation and antioxidant status with preeclampsia quantitatively using meta-analysis. Systematic review and meta-analysis. Studies were identified by performing an extensive search using BIOSIS (1986-2007), EMBASE (1986-2007), Medline (1986-2007), and the Cochrane database. Standardized mean differences (SMD) with 95% confidence intervals (CI) were used in the meta-analysis and sources of heterogeneity were examined. In the included studies, the overall SMD was a 1.21 nmol/mL increase in serum malondialdehyde in preeclampsia cases compared to controls (95% CI: 0.76, 1.66). Overall, total serum thiobarbituric acid-reactive substances SMD were 1.62 nmol/mL greater in cases than in controls (95% CI: 0.27, 2.96). The overall estimate SMD for serum vitamin E was 1.12 nmol/mL less in cases than controls (95% CI: -1.77, -0.48) and vitamin C SMD overall estimate was -0.53 (95%CI: -1.03, -0.02), significantly lower in cases compared with controls. The overall SMD for erythrocyte superoxide dismutase was -2.37 (95% CI: -4.76, 0.03), a marginally significant decrease in cases versus controls. Established preeclampsia is associated with increased concentrations of oxidative stress markers including lipid peroxidation products, and a reduction in antioxidant concentrations. Obstetricians & Gynecologists, Family Physicians. After completion of this educational activity, the participant should be better able to describe the pattern of oxidative stress markers associated with preeclampsia, and interpret the available literature as it relates to oxidative stress and preeclampsia.