Youth homelessness is a serious concern. Evidence shows that youth who experience homelessness are at high risk of exposure to a range of physical and mental health problems, violence, early pregnancy, and early death. However, efforts to solve the problem have been constrained by the absence of credible data on the size and characteristics of the population and reliable means to track youth homelessness over time. In response, this study was undertaken as part of Voices of Youth Count (VoYC), a national research initiative on youth homelessness led by Chapin Hall at the University of Chicago. The research was designed to address critical evidence gaps while also responding to the federal Runaway and Homeless Youth Act (RHYA; P.L. 110–378), which calls for replicable national prevalence and incidence estimates of youth homelessness and data concerning the population's needs and characteristics.