Hereditary breast cancer accounts for less than 5-10% of breast cancers diagnosed each year in the United States. Despite the low prevalence, inheritance of a gene mutation is associated with a high risk of developing breast and other cancers. Research into alterations of BRCA1 and BRCA2 as well as other breast cancer genes remains a high priority for scientists and for men and women who are potential carriers of a mutation. This research is important to understand the pathogenesis of breast cancer in this select population, to determine whether these findings may be applicable to women with familial or sporadic breast cancer, and to develop specific biologic or drug therapies targeted at the underlying causative mechanism. Certain mutations are more common in selected ethnic groups, which may also be important in assessing risk or developing new treatments. This presentation will summarize the current state of knowledge of the molecular biology of BRCA1 and BRCA2, the prevalence and penetrance of mutations in these genes, the technical aspects of genetic testing, and the current state of knowledge of drug therapy for these lesions.