Hormone replacement therapy for postmenopausal women greatly reduces their risk of coronary heart disease. However, current pharmaceutical regimens have a low acceptance rate among postmenopausal women. We have sought to identify an alternative treatment that would retain the beneficial health effects of current standard therapy without its negative aspects. We have concentrated our research on naturally occurring estrogens (called phytoestrogens) found in soybeans, in the belief that delivery of phytoestrogens via the diet would be more acceptable than pharmaceutical regimens. Using a well-established nonhuman primate model of postmenopausal women, we have investigated the effects of soy phytoestrogens on cardiovascular risk factors and the reproductive system. In this review, we summarize the results of our ongoing research.