Oxidative stress is believed to be a cause of aging and cardiovascular disorders. In response to inflam-mation or endothelial cell injury, production of reactive oxygen species (ROS) is enhanced in vascular cells. These changes contribute to the initiation of atherosclerosis. Vascular cells possess anti-oxidant systems to protect against oxidative stress, in addition to the redox system. The redox status of pro-tein thiols is important for cellular functions. The Akt signaling pathway exerts effects on survival and apoptosis, and is regulated by the glutathione (GSH)/glutaredoxin (GRX)-dependent redox sys-tem. Sex hormones such as estrogens protect against oxidative stress by protecting the Akt signaling pathway but the physiological role of the extracellular GSH/GRX system has not been clarified, although found an increase in the levels of S-glutathionylated serum proteins in patients with athero-sclerosis obliterans. The results suggested that impaired serum redox potential is a marker of the development vascular dysfunction and estrogen has a possible role in the prevention of atherosclerosis.