Women in the United States have a 12% lifetime risk of developing breast cancer. Although only about 5% to 10% of all cases of breast cancer are attributable to a highly penetrant cancer predisposition gene, individuals who carry a mutation in one of these genes have a significantly higher risk of developing breast cancer, as well as other cancers, over their lifetime compared with the general population. The ability to distinguish those individuals at high risk allows health care providers to intervene with appropriate counseling and education, surveillance, and prevention-with the overall goal of improved survival for these individuals. This article focuses on the identification of patients at high risk for breast cancer and provides an overview of the clinical features, cancer risks, causative genes, and medical management for the most clearly described hereditary breast cancer syndromes. Newer genes that have also been implicated in familial breast cancer are also briefly reviewed.