This journal article describes a study conducted to address gaps in the credible data on the size and characteristics of the unaccompanied, homeless youth population in the U.S. Using a nationally representative phone-based survey (N=26,161), the researchers solicited household and individual reports on different types of youth homelessness. Household reports on adolescents aged 13-17 and young adults aged 18-25, as well as self-reports from young adults aged 18-25, were collected. Follow-up interviews with a subsample of 150 respondents provided additional information on youth experiences and enabled adjustment for inclusion errors. Results indicate that over a 12-month period, approximately 3.0 percent of households with 13- to 17-year-olds reported explicit youth homelessness (including running away or being asked to leave) and 1.3 percent reported experiences that solely involved couch surfing, resulting in an overall 4.3 percent household prevalence of any homelessness. For 18- to 25-year-olds, household prevalence estimates were 5.9 percent for explicitly reported homelessness, 6.6 percent for couch surfing only, and 12.5 percent overall. The 12-month population prevalence estimates, available only for 18- to 25-year-olds, were 5.2 percent, 4.5 percent, and 9.7 percent, respectively. Prevalence rates were similar across rural and nonrural counties. Higher risk of homelessness was observed among young parents; black, Hispanic, and lesbian, gay, bisexual, or transgender youth; and those who did not complete high school. The prevalence and incidence of youth homelessness reveal a significant need for prevention and youth-centric systems and services, as well as strategies to address disproportionate risks of certain subpopulations. (Author Abstract Modified)