OBJECTIVE A deficiency in superoxide dismutase (SOD) activity in preeclamptic placentas can lead to an excess of superoxide radicals and may be responsible for the development and the severity of preeclampsia (PE). METHODS Our studies were undertaken in order to determine placental SOD activity and to investigate their association with the development and the severity of PE. METHODS The activity of SOD was determined using a spectrophotometric method in 22 placentas from normal term pregnancies (group K), 24 placentas from pregnancies complicated by severe PE (group PE), and 21 placentas from pregnancies complicated by severe PE and intrauterine growth retardation (IUGR) (group PEI). RESULTS Mean activity of SOD (MSOD) in 45 preeclamptic placentas 3.89 +/- 1.32 (M +/- SD) was significantly lower (P = 0.008) as compared to MSOD in the group K (6.75 +/- 1.96). MSOD in the PEI group (3.5 +/- 1.29) was significantly lower (P = 0.03) as compared to MSOD in the group K. MSOD in the PE group (4.23 +/- 1.25) was lower than MSOD in the group K, but this difference was not statistically significant (P = 0.11). MSOD in the group PEI was lower as compared to MSOD in the PE group, however this difference was not statistically significant (P = 0.23). CONCLUSIONS The studies revealed decreased SOD activity in preeclamptic placentas in comparison to normal placentas.