Abstract Objectives: To evaluate the total isoprostane 8-epi-PGF2α and neutrophil elastase (NE) concentrations in pregnancies complicated by premature rupture of membranes (PROM). Material and methods: 128 pregnant women were divided into four groups: pregnancies complicated by PROM between 24.-36.(PPBP-N) and between 38 a 41 weeks of gestation (PPBP-D), uncomplicated pregnancies between 24-36 gestation weeks (K1) and pregnancies delivered by cesarean section (before uterine contractions had started) after 38 weeks (K2). The concentrations of NE and isoprostane 8-epi-PGF2α were measured in maternal serum, cord blood serum and in the amniotic fluid. Results: The following study revealed higher concentrations of NE in maternal serum and in the amniotic fluid than in the umbilical cord blood in PROM cases, and lower amniotic fluid than maternal serum concentrations in the control groups. Also, the levels of isoprostane differentiated between compartments in particular groups. In both groups complicated with PROM, higher maternal serum and amniotic fluid NE concentrations than in controls were found. There were no differences in isoprostane levels between the groups. Conclusions: 1. Higher concentrations of NE in maternal blood serum and in the amniotic fluid than in the umbilical cord blood in PROM cases, as well as lower amniotic fluid than maternal serum concentrations in the controls, may be connected with pathogenesis of PROM. 2. Differentiated maternal serum, cord serum and amniotic fluid isoprostane concentrations may suggest various intensity of oxidative stress in particular compartments. 3. Lack of differences in maternal serum, cord serum and amniotic fluid isoprostane concentrations may suggest similar intensity of oxidative stress in cases with PROM and intact membranes.