Hereditary breast and ovarian cancer syndrome is an inherited cancer-susceptibility syndrome. The hallmarks of this syndrome are multiple family members with breast cancer or ovarian cancer or both, the presence of both breast cancer and ovarian cancer in a single individual, and early age of breast cancer onset. Clinical genetic testing for gene mutations allows physicians to more precisely identify women who are at substantial risk of breast cancer and ovarian cancer. For these individuals, screening and prevention strategies can be instituted to reduce their risks. Obstetricians and gynecologists play an important role in the identification and management of women with hereditary breast and ovarian cancer syndrome.