Evidence-based guidelines recommend that persons at elevated risk of cancer begin cancer screening at a younger age than the general population and consider more sensitive screening tests. A family history of cancer contains powerful information for cancer risk stratification.1 Because most common cancers are diagnosed in older age, the prevalence of a family history of cancer increases throughout adulthood. However, age-specific data based on detailed family history have only recently become available.2 In this issue of JAMA, Ziogas and coinvestigators from the Cancer Genetics Network (CGN)3 report prospective and retrospective data from a population-based registry to illustrate the extent to which family history relevant for cancer prevention increases with age. What are the implications for preventive care?