Breast cancer is a common type of cancer among women in the United States. Despite improvements in early detection and treatment, about 39,600 American women will die of breast cancer in 2002. Chemoprevention is a strategy for reducing the risk for cancer (“prevention”) by taking drugs (“chemo”). The drug tamoxifen reduces the risk for a second episode of breast cancer in women who have already had breast cancer. Some evidence indicates that tamoxifen and a similar drug, raloxifene, can prevent breast cancer in women who have never had the disease. Of note, the U.S. Food and Drug Administration has approved only tamoxifen for the prevention of breast cancer. However, these drugs also have side effects that include hot flashes, vaginal discharge, and sexual problems, and they increase the risk for cancer of the uterus, stroke, cataracts, and blood clots. Women must weigh the potential benefits of chemoprevention for breast cancer against these risks of taking the drugs.