Inherited mutations in BRCA1 and BRCA2 predispose to extremely high risks of breast and ovarian cancer. But these risks are not immutable. Among women who carry mutations in BRCA1 or BRCA2, surgical intervention, in particular risk-reducing salpingo-oophorectomy, reduces risk of both ovarian and breast cancer and reduces overall mortality. However, many women with mutations in these genes are identified as carriers only after their first cancer diagnosis because their family history of cancer was not sufficient to suggest genetic testing. To identify a woman as a carrier only after she develops cancer is a failure of cancer prevention. Here, King et al describe the application of the discovery of a single gene BRCA1 that causes a form of hereditary breast cancer and suggest that population-based screening of women for BRCA1 and BRCA2 should become a routine part of clinical practice.