Breast cancer is the most common cancer and the second most common cause of cancer death in women. In 2008 there were 182,460 women diagnosed with breast cancer, and 40,480 women died of this disease. Breast cancer can be prevented by medical (tamoxifen or raloxifene) or surgical approaches (bilateral mastectomy or oophorectomy). Prevention is only recommended for women at high risk for developing breast cancer; therefore, proper risk calculation is essential in identifying women that may benefit from prevention measures. There is an easy-to-use and easily accessible risk calculation tool for determining a woman's risk of developing breast cancer and need for referral for counseling, gene testing, and possibly preventive therapy. This article reviews the components of risk assessment, the most frequently used risk calculation tool, and approaches to breast cancer risk reduction including medical and surgical therapies. The use of these therapies results in a risk reduction of 50-90%.