The active ingredient in a drug used to reduce the risk of invasive breast cancer in postmenopausal women who are at high risk of the disease or who have osteoporosis. It is also used to prevent and treat osteoporosis in postmenopausal women. Raloxifene is also being studied in the treatment of other types of cancer. It blocks the effects of the hormone estrogen in breast tissue, which may help keep breast cancer cells from growing. It may also help keep bone from breaking down. Raloxifene is a type of selective estrogen receptor modulator (SERM).