Preventing and ending homelessness requires actions at multiple levels. HOD researchers have contributed by analysing the structural causes of homelessness and their links to social exclusion, by empirical work with collaborators and policy engagement at the national and local levels. A national 12-site experiment examines what interventions work best to end homelessness for families. Qualitative interviews help to understand families’ experiences, their access to supports, the ways they make housing decisions, and the ways that programs separate family members from one another. Work in New York City and Alameda County California helps homeless service administrators target prevention services to people who can derive greatest benefit from them and evaluates a prevention program. Local work in Nashville responds to needs identified by the homeless service system.