Aim — to evaluate the condition of lipid peroxidation and antioxidant defense systems in patients with pelvic organ prolapse. Material and methods. Sixty women were examined, the average age of which was 46.0±1.5 years. The first group (control) included 30 women without somatic or gynecological pathology. The second group included 30 patients with a diagnosis of prolapse of the uterus and walls of the vagina of I—II degree. The intensity of lipid peroxidation was determined in all patients by the method of induced chemiluminescence of blood serum, the number of primary (diene conjugates) and final (Schiff bases) molecular products of lipid peroxidation was measured, and the activity of superoxide dismutase and catalase enzymes in the blood was determined. Results. In patients with prolapse of the uterus and vaginal walls, the Imax level was 1.75 times higher than in healthy ones, the S index — 1.79 times higher, tg 2α — 1.65 times higher (p<0.05 in all cases ). Diene conjugates and Schiff bases values in the second group of patients exceeded the corresponding values of the control group by 2 times (p<0.05 in both cases). In patients with prolapse, catalase activity was 1.26 times lower and superoxide dismutase — 1.29 times lower than in healthy women (p<0.05 in both cases). Conclusion. Antioxidant deficiency and peroxide stress are the factors in the pathogenesis of pelvic organ prolapse at the systemic level, which creates pathogenetic prerequisites for the inclusion of exogenous antioxidants or agents that stimulate the endogenous antioxidant defense system in the complex of therapeutic and preventive measures in this group of patients.