ABSTRACTUterine leiomyomas are benign soft-tissues tumors that arise from uterine smooth muscle tissue. Etiopathogenesis of leiomyomas is not well understood. We aimed to examine whether antioxidant enzyme activities and lipid hydroperoxides level in patients with leiomyoma are influenced by changes in sex hormones and gonadotropins (estradiol (E2), progesterone, FSH, and LH) during menstrual cycle and in postmenopause. The material consisted of blood and uterine tissue specimens. Hormone concentrations were determined and assays for superoxide dismutase, catalase, glutathione peroxidase and glutathione reductase activities and lipid hydroperoxides concentration were performed. In blood of examined women, a significant difference in catalase, glutathione peroxidase and glutathione reductase activity was recorded among the phases. There was also a positive correlation between the estradiol/progesterone concentration and the catalase activity. Progesterone negatively correlated with lipid hydroperoxides level. In myoma tissue, we recorded a phase-related difference in lipid hydroperoxides level and activities of superoxide dismutase, glutathione peroxidase activities, and glutathione reductase. Negative correlation was observed between FSH and glutathione peroxidase. The results suggest that antioxidant status in patients with uterine leiomyoma is influenced by the changes in sex hormones during the menstrual cycle and in postmenopause, indicating a role of the observed relationship in the leiomyoma etiology.