Tamoxifen was approved for breast cancer prevention in October 1998. Thus, for 
the first time, we as gynecologists are being asked to prescribe this drug to 
healthy women. In the past each one of us has cared for women with breast cancer 
who have been treated with tamoxifen by oncologists or breast surgeons for the 
malignancy. Effects of tamoxifen on the uterus resulting in carcinomas, 
hyperplasia, and polyps are well known. Furthermore, tamoxifen has estrogenic 
properties in the venous system, increasing the incidence of deep vein 
thrombosis and pulmonary emboli. A new SERM (selective estrogen receptor 
modulator), raloxifene, has been approved for prevention and treatment of 
osteoporosis in postmenopausal women. It does not have stimulatory effects on 
the endometrium; however, it is estrogenic in the venous system. Preclinical 
data, as well as the breast cancer incidence reported in studies of the 
skeleton, seem to indicate that its effects in the breast are similar to those 
of tamoxifen. This article reviews tamoxifen and the new SERM, raloxifene, in an 
attempt to help gynecologists better understand each compound and what data are 
currently known, what we hope to learn from future studies, and what currently 
makes sense for clinical practice.