The aim of the study was to investigate antioxidant status, monitored by selenium and thiobarbituric acid-reactive substance concentrations in blood plasma, and glutathione peroxidase activity in erythrocytes and blood plasma in women with gestosis (n = 26), imminent premature labour (n = 48) and normal pregnancy (n = 23) during 19-38 weeks of pregnancy. Selenium concentrations in blood plasma were significantly higher in women with pathological pregnancies than in normal (45.5 +/- 10.5 micrograms l-1, p < 0.01 and 44.1 +/- 11.6 micrograms l-1, p < 0.05 vs. 38.6 +/- 8.3 micrograms l-1, respectively). In all groups of pregnant women Se concentrations were extremely low as compared with non-pregnant females. Glutathione peroxidase (GSH-Px) activity in blood plasma was significantly higher in complicated pregnancies than in healthy ones. There were no significant differences in thiobarbituric acid-reactive substance concentrations between all groups of pregnant women. Statistically significant correlations were found between blood plasma Se concentrations and GSH-Px activity in healthy pregnant (r = 0.53, p < 0.01), imminent premature labour (r = 0.39, p < 0.01), and non-pregnant females (r = 0.56, p < 0.001).