Multiple factors which increase a women's breast cancer risk have been identified. These range from conditions such as lobular carcinoma in situ which increase risk to relatively high levels, to reproductive factors such as nulliparity which are associated with only a small increase in risk. When determining an individual's risk, all her potential breast cancer risk factors must be considered. In order for risk information to be meaningful to a woman, risk must be expressed as absolute risk over a defined time interval since there is no uniform agreement on what risk level is high enough to require intervention. At present, careful follow-up or prophylactic mastectomy are the management options available for the woman at increased risk. The efficacy of follow-up including breast self exam, physician exams, and screening mammography for early detection of cancer in a high risk population is unknown. Prophylactic mastectomy, while highly effective, does not provide complete protection from breast cancer and is more radical than the surgery done for established cancer in many cases. Which of these options is chosen by an individual woman is dependent on how much risk she is willing to assume.