To the Editor On behalf of my coauthors, I write to report errors that occurred in the Original Investigation, “Population-Attributable Risk Proportion of Clinical Risk Factors for Breast Cancer,” that was published in the September 2017 issue of JAMA Oncology.1 In that article, we reported the findings of a population-based case-control study with matching on age, year of risk factor assessment, and Breast Cancer Surveillance Consortium registry. The study objective was to determine the population-attributable risk proportion (PARP) for breast cancer associated with clinical breast cancer risk factors among premenopausal and postmenopausal women.