Observations of the pharmacology of tamoxifen and related compounds have lead to the concept of selective estrogen receptor modulators (SERMs). This new class of drug displays estrogen agonist or antagonist effects in a tissue-dependent manner and appears to offer an alternative to hormone replacement therapy for the prevention and treatment of osteoporosis and cardiovascular disease in postmenopausal women. Moreover, the estrogen antagonist actions of SERMs on breast tissue may also provide a protective effect against breast cancer. Although tamoxifen therapy reduces plasma cholesterol levels and maintains bone density, it is also associated with an increased risk of endometrial cancer, pulmonary embolism and deep vein thrombosis. This has lead to the development of newer SERMs which will hopefully lack these adverse effects of tamoxifen. These compounds promise a new era of disease prevention in the aging woman and their therapeutic potential is currently being evaluated in large-scale clinical trials.