Accurately estimating the incidence, prevalence, and composition of the population of Veterans who experience homelessness is important for planning and evaluating prevention and intervention strategies. However, several methodological considerations exist that are relevant to establishing and interpreting epidemiological estimates of homelessness among Veterans. These issues include the conceptual definition of homeless and Veteran status; the various time frames used in enumeration efforts and the implications of these time frames on resulting estimates; and the strengths and limitations of primary and administrative data sources. This chapter discusses methodological issues and present a national epidemiological estimates based on various sources and methodologies. Recent point prevalence, period prevalence, and incidence estimates are summarized, as are segmentation of estimates by demographic, geographic, and housing status characteristics, and trends over time. In the past decade, several indicators have suggested that homelessness among Veterans has decreased substantially. Since 2009, point-in-time estimates have declined nearly 50%, and 1-year estimates have declined by 11%. Despite these improvements, Veterans continue to be overrepresented among the population of homeless adults in the United States.