This year's "America's Children in Brief: Key National Indicators of Well-Being" continues more than a decade of dedication and collaboration by agencies across the Federal Government to advance our understanding of our Nation's children and what may be needed to bring them a better tomorrow. "America's Children in Brief, 2018" uses both established and previously untapped data sources to characterize vulnerable children across several of the domains included in the Forum's conceptual framework. The measures included provide emerging insight on children who face special and heightened risks to their well-being. Each section of the report addresses why the measure of at-risk children is important and presents information on characteristics of the population of at-risk children. In addition to providing descriptive information on trends on the size of the population ages 0 to 17, this year's report features the following measures: (1) Poverty and extreme poverty; (2) Health insurance continuity; (3) Homelessness; (4) Exposure to violence; (5) Prescription opioid misuse and use disorders; and (6) Residential placement of juveniles. [For the 2016 "Brief," see ED590231. For "America's Children: Key National Indicators of Well-Being, 2017," see ED577338.]