Abstract: Background: Exposure to ETS (Environmental Tobacco Smoke) is one of the most toxic environmental exposures. Objective: To investigate the impact of ETS on physiological, biochemical, psychological indicators, on the urine antioxidant capacity (AC) and oxidative damage to lipids in a pilot sample of healthy pregnant women. Methods: The exposure to ETS was investigated by a validated questionnaire, urine cotinine and the marker of oxidative damage to lipids - 8-isoprostane concentrations using an ELISA kit. Urine AC was determined by the spectrophotometric TEAC method. From the sample of pregnant women (n=319, average age 30.84 ± 5.09 years) in 80 the levels of cotinine and oxidative stress markers were analyzed. Results: From our sample, 5 % individuals (7.4 % objectified by cotinine) were current smokers and 25 % reported passive smoking in the household (18.8 % objectified by cotinine). The Kappa was 0.78 for smokers and 0.22 for ETS exposed non-smokers. Smokers as well as non-smokers had significantly higher (p<0.05) urine AC than ETS exposed non-smokers. Non-smokers had significantly lower levels of 8-isoprostane than smokers (p<0.01) and ETS-exposed non-smokers (p<0.05). Correlations between urine levels of cotinine and AC were positive in ETS exposed non-smokers. Conclusion: The harmful effect of active and passive smoking on oxidative stress parameters has been indicated.