 Raloxifene is a drug that is related to estrogen. In the liver and bone, it acts like estrogen. In the breast and uterus it acts like an anti-estrogen. It has been used in postmenopausal women to prevent a disease called osteoporosis. This is a disease that decreases bone strength over many years and may finally lead to bone fractures. In a group of women who were taking the drug, it also seemed to decrease the chances of breast cancer and possibly endometrial cancer cancer of the uterus. Therefore, we want to study it further to see if it prevents breast cancer. We also want to find out if it may be even better in preventing breast cancer if it is given with another drug. 