While many individual risk factors have been defined for breast cancer, a family history was recognized long ago as one of the most potent. Mutations within BRCA1 or BRCA2, both identified about 10 years ago, are responsible for the majority of inherited breast cancer. By virtue of her age alone, a young woman diagnosed with breast cancer has a greatly elevated probability to carry a BRCA mutation. Other risk factors, including a personal or family history of ovarian cancer, bilateral breast cancer or Jewish ancestry, only serve to increase that chance. It is critical that clinicians caring for a young woman understand their patient's elevated risk to carry such a mutation and thoughtfully investigate this risk. Upon identification of a mutation in a young woman there are many consequences which necessitate careful consideration of various treatment and preventative options including prophylactic mastectomy and oophorectomy. Finally, the diagnosis of breast cancer in a young woman and the attendant genetic implications have immediate and serious consequences for her family members. Genetic professionals can help navigate the complex technical and psychosocial issues. This chapter explores the molecular, clinical and ethical intricacies of BRCA genetic testing.