Most breast and ovarian cancers occur sporadically, but an estimated 5 to 10% of cases occur in women with hereditary predisposition to these cancers. Two genes,BRCA1andBRCA2, have been identified, which, when altered, are thought to be responsible for most cases of hereditary breast and ovarian cancer. Testing for mutations in these genes is now available for women who are at risk. At present, only a small percentage of women have been tested, and identification of high risk women is dependent on pedigree analysis and application of empiric models.In the general population, the level of risk of hereditary cancer ranges from nonexistent to highly likely. A disease management approach requires identification of the level of risk of each individual in the population, and the development of a specific management strategy of screening and consideration of chemoprevention and prophylactic surgery commensurate with risk. Therefore, risk identification takes on an important role in the allocation of health resources.This article presents an approach to categorising women who are at increased risk of experiencing hereditary breast or ovarian cancer, whether or not testing is accepted or feasible. An evidence-based approach to screening and measures for prevention are outlined according to level of risk. Occasions when genetic testing would appreciably enhance decisions regarding management are noted.Clinically useful guidelines for risk assessment and management are intended to reduce the incidence of and morbidity associated with hereditary breast and ovarian cancer. Ongoing research with regard to clinical outcomes of carriers of theBRCA1orBRCA2mutation will help refine these strategies.