This report explores Housing First in relation to the evidence base on services designed to end homelessness among single people (i.e. lone adults) with support needs. Some attention is given to prevention and relief services, but this report is concerned with services for those single homeless people who require support as well as housing. The report does not encompass services for homeless families. 

The report has four main objectives: 

• To critically assess the evidence base for Housing First and other homelessness services, considering the extent to which the case for different service models has been proven or disproven. 
• To consider the state of the evidence on the efficiency and cost-effectiveness of different service models.
•  To review the potential for different service models to contribute to an effective, integrated strategy to prevent homelessness and to minimise the risk of homelessness becoming prolonged or recurrent. 
• To consider how lessons from various service models might be employed to increase the efficiency and effectiveness of homelessness services as a whole. 

Globally, the existing evidence shows that integrated homelessness strategies that encompass effective homelessness prevention, rapid re-housing systems for when homelessness first occurs and a range of housing related support services for homeless people with high and complex needs – which includes Housing First working in coordination with other services – can deliver a ‘functional zero’ in homelessness.  The Finnish, Danish and Norwegian strategies show what can be achieved with the use of Housing First within a coordinated, integrated homelessness strategy which includes a mix of service models. 

Crucially, these strategies have shown success by using Housing First alongside a mix of other models of floating (mobile) support and fixed-site supported housing, including congregate and communal models. This review explores the ways in which Housing First and other services are best employed within integrated homelessness strategies. 

The report begins by looking at how changes in the understanding of homelessness and its financial, as well as social, costs have led to the development of new service models and to the emergence of integrated strategic responses to homelessness. The following section then critically explores the evidence base for different service models, including Housing First. 

Finally, the report considers the lessons from the evidence to discuss what the optimal mix of services within an effective homelessness strategy should look like, and how the key lessons and successes from different models of homelessness service might be used to enhance the prevention and ending of homelessness.