The purpose of this study was to characterize prooxidant-antioxidant balance in patients with different clinical types of spontaneous abortion. Sixty previously untreated, pregnant women aged 16-38 years were included into this study. The gestational age ranged from 8 to 12 weeks. Patients were divided into three groups of 20 subjects each. The first group consisted of patients with inevitable abortion. The second group included women with threatened abortion in whom pregnancy was maintained until term. The control group consisted of women with uncomplicated pregnancy. In all the patients venous blood was collected immediately after the diagnosis was settled and before the treatment was commenced. Two biochemical markers of oxidative stress were quantified, namely: lipid peroxides (LP) using spectrophotometric TBARS method and total antioxidant status (TAS) by means of the commercially available kits (TAS: Randox Laboratories Ltd., U.K.). The obtained results indicate that spontaneous abortion is accompanied by a profound disruption of the prooxidant-antioxidant homeostasis towards oxidative stress.