Objective: A number of studies have consistently shown a lower cardiovascular risk in women who received postmenopausal hormone replacement therapy (HRT). The aim of our study was to examine the effects of HRT on lipid peroxidation and antioxidant status, which were likely to be involved in the pathophysiology of atherosclerosis. :Methods: We measured erythrocyte and plasma thiobarbituric acid reactive substances (TBARS) levels as expression of lipid peroxidation-end product malondialdehyde, and also erythrocyte reduced glutathione (GSH) level and glutathione peroxidase (GSH-Px) activity as indicators of the antioxidant status of the 35 postmenopausal women with HRT (mean age: 51.81 +/- 4.57 yr: body mass index (BMI): 26.56 +/- 3.78 kg/m(2)) and 35 postmenopausal women without HRT (mean age: 47.50 +/- 3.64; BMI: 27.42 +/- 3.43 kg/m(2)). Results: In the group with HRT, erythrocyte and plasma TBARS levels were significantly lower than in the group without HRT (P < 0.003 and P < 0.001, respectively). Erythrocyte GSH level and GSH-Ps activity was found to be increased significantly in the group with HRT in comparison with the group without HRT (P < 0.001 and P < 0.001, respectively). There was not any correlation between the erythrocyte and plasma TBARS and erythrocyte GSH levels and GSH-Px activity with duration of HRT (mean 3.5 +/- 1.3 yr). Conclusion: Our results show that HRT is beneficial in thr protection against oxidative damage and can prevent atherosclerotic complications. (C) 2001 Elsevier Science ireland Ltd. All rights reserved.