Raloxifene (Evista) is now approved for use as prophylaxis to diminish the risk of breast cancer in postmenopausal women with osteoporosis and in postmenopausal women at high risk for invasive breast cancer. Raloxifene, a selective estrogen receptor modulator previously approved for treating and preventing osteoporosis in postmenopausal women, works, it is thought, by blocking estrogen receptors. Clinical trial data submitted to the Food and Drug Administration showed that the drug is effective as prophylaxis and that its effects are comparable to those of tamoxifen (Nolvadex, Soltamox), a nonsteroidal antiestrogen product and formerly the only drug approved for the prevention of breast cancer. Like tamoxifen, raloxifene poses the risk of serious adverse effects including blood clots and stroke, but a lower risk of uterine malignancies. Health care practitioners should note that the expected benefits of raloxifene and the risks posed in its use should be carefully evaluated for each patient, and that the drug does not prevent breast cancer completely.