In 2009, President Obama and Secretary Shinseki committed to ending homelessness among Veterans. In support of that effort, the Federal Strategic Plan to Prevent and End Homelessness 2010 developed by the United States Interagency Council on Homelessness (USICH) established as one of its goals to prevent and end homelessness among Veterans in five years. An understanding of the epidemiology of homelessness among Veterans and the methodological strengths and weaknesses of this evidence base may inform program-planning efforts and future research needs. Understanding the risk factors for homelessness among Veterans and how these risk factors compare to the general population is important in developing identification and prevention programs for Veterans at risk for homelessness. This report was requested by VA Central Office and The National Center for Homelessness Among Veterans as part of that effort to identify what is known and what is not known about the prevalence of homelessness among Veterans, and about the risk factors for homelessness among Veterans, including risk factors related to military service and incarceration. The key questions were: Key Questions #1a. What is the prevalence and incidence of homelessness among Veterans? #1b. How has the prevalence and incidence of homelessness among Veterans changed over time? #1c. How prevalent are psychiatric illness, substance abuse, and chronic medical illness among homeless Veterans? Key Questions #2a. Which risk factors are associated with new homelessness or a return to homelessness among Veterans? How do these risk factors differ from non-Veteran populations? #2b. Have risk factors for homelessness among Veterans changed over time? Key Question #3. Are there factors specific to military service that increase the risk of homelessness, or is the increased risk a marker for pre-military comorbidities and social support deficiencies? Key Question #4. What is the relationship between incarceration and homelessness among Veterans?