The relative lack of standards for collecting data on population subgroups has not only limited our understanding of health disparities, but also impaired our ability to develop policies to eliminate them. This article provides background about past challenges to collecting data by race/ethnicity, primary language, sex, and disability status. It then discusses how passage of the Affordable Care Act has provided new opportunities to improve datacollection standards for the demographic variables of interest and, as such, a better understanding of the characteristics of populations served by the U.S. Department of Health and Human Services (HHS). The new standards have been formally adopted by the Secretary of HHS for application in all HHS-sponsored population health surveys involving self-reporting. The new data-collection standards will not only promote the uniform collection and utilization of demographic data, but also help the country shape future programs and policies to advance public health and to reduce disparities.