Recently, olaparib(brand name: Lynparza Tablets)-a PARP inhibitor-has been approved for national health insurance coverage in Japan as a drug for unresectable or recurrent, BRCA1/2-positive, HER2-negative breast cancer in patients with a history of cancer chemotherapy. The addition of BRCA1/2 genetic testing as a companion diagnostic tool to the health insurance coverage is of considerable significance as a spearhead of health insurance medical care for all different types of hereditary tumors. However, several problems related to this companion diagnostic test have emerged, including the estab- lishment of a genetic counseling system and handling of BRCA1/2 genetic tests performed at the patients' own expense. In addition, the purpose of the companion diagnostic test is to confirm drug indication in a case. However, since the test results include the diagnosis of hereditary tumors, there is also an urgent need to improve the medical care system and social environment for family members of patients with pathological mutations. The use of genetic analysis is widespread in the clinical settings, and genetic medical care is anticipated to advance in the future. Therefore, it would be pivotal to come up with measures against hereditary tumors, such as hereditary breast and ovarian cancer(HBOC)syndrome. In this chapter, we describe the current status and prospects of HBOC medical care, with a particular focus on companion diagnostics.