Starting even before the identification of the BRCA1 and BRCA2 cancer susceptibility genes, several models were well established as predictors of a woman's risk of inherited breast cancer.1 During the past decade, these models have been refined not only to predict breast cancer risk, but also to predict the likelihood that an individual carries a deleterious mutation in one of these genes. Such models have been used as criteria for offering genetic testing,2 for determining eligibility for screening and prevention trials,3 and, increasingly, for assessing appropriateness of participation in incremental risk-reduction strategies.4,5 Illustrating the influence modeling is having on clinical practice, the American Cancer Society recently issued guidelines for offering screening breast magnetic resonance imaging, which, among other criteria, stated that women with a lifetime risk of breast cancer of “20-25% or greater, as determined by BRCAPRO or other models that are largely dependent on family history,” should be offered annual breast magnetic resonance imaging beginning at age 30 years.4