Background: Evidence is accumulating that mitochondrial (Mt) oxidative stress plays a role in the pathogenesis of preeclampsia. The current study analyzes the stress levels, energy status and associated enzymatic alteration in placental mitochondria of preeclamptic (ns30) and normotensive (ns35) subjects. Methods: Total Mt stress was measured using dichlorofluorescin (DCFH) oxidant analysis, malondialdehyde (MDA) concentrations, protein carbonyl (PC) concentrations and measurement of nitrite ( ) and