The effects of menopause on antioxidant enzyme activities were investigated in blood and endometrial tissues of women. Endometrial pieces were obtained from pre-or postmenopausal patients who had hysterectomy due to descendus or prolapsus uteri. In endometrium homogenates, both cytosolic superoxide dismutase (CuZn-SOD) and catalase (CAT) activities were similar in pre-or postmenopausal women (median ages 41 and 64, respectively); whereas GPx (glutathione peroxidase) activity was significantly decreased (p< 0.001). Activity of these enzymes were also compared in the blood of premenopausal and late menopausal women, and only GPx activity was found significantly low (p< 0.01). Subsequent measurements were carried out in blood of healthy menopausal women who were in the same age intervals with the premenopausal subjects studied, and GPx activity was found indifferent in two groups, indicating that the decrement is due to aging rather than the change in hormonal status. CuZn-SOD activity was highest in blood of late menopausal group compared with those in both premenopausal and early menopausal group, giving a significant difference with the latter (p< 0.001). In other words, SOD activity was increased in menopausal women at an older age, showing a diverse change with GPx activity.