The hormonal therapy (HT) is recommended for postmenopausal women primarily for the relief of vasomotor symptoms, treatment of vaginal atrophy, and prevention of osteoporosis. Despite these important benefits, only 35% to 40% of the women ever start HT, and many do not continue it. The reasons for discontinuation include resumption of bleeding, perceived risks of breast cancer, unacceptable side effects and the belief that treatment is no longer necessary. As a result, there is an increasing interest in the use of plant-derived estrogens, also known as phytoestrogens, which seem to be very promising. Isoflavones is the most investigated subgroup of phytoestrogens. They are attenuated estrogens and behave both in vivo and in vitro as agonists and antagonists. The highest concentrations of isoflavones are found primarily in soy beans. In this study, the effects of soy isoflavones on postmenopausal women were reviewed.