We aimed to determine the value of maternal erythrocyte malondialdehyde levels in the prediction of preeclampsia. 110 healthy women were included in this prospective study.Maternal erythrocyte malondialdehyde levels were measured at each trimester of pregnancy (10-14, 20-25 and 3035 gestational weeks). On followup, patients were assigned to two groups as normotensive women and preeclamptic patients. Preeclampsia had developed in eight (8.9%) of the 90 pregnant women who completed the study. Preeclamptic patients were diagnosed between 36 and 39 gestational weeks (36.8+/-1.0 weeks). Malondialdehyde levels of preeclamptic patients increased significantly in the third trimester (p < 0.05), while there was no difference between values of malondialdehyde in the first and second trimester. Malondialdehyde levels were significantly higher in the patients who developed preeclampsia than in those who did not in the third trimester (p < 0.05).With the use of the receiver operating characteristics (ROC) 35.98 nmol malondialdehyde/gm hemoglobin was found to be a cutoff value predictive for the development of preeclampsia in the third trimester.However, cutoff values in the first and second trimesters could not be found.The sensitivity, specificity, positive and negative predictive values were 89, 75, 29 and 98%, respectively. Preeclampsia risk was found to increase nearly 24 times in values above 35.98 nmol malondialdehyde/ gm hemoglobin.