The concept of trans-institutionalization refers to the transfer from one type of institution providing services for people with a disability, such as state psychiatric hospitals, to another type of institution providing services such as prisons. It is possible to correct these circumstances as there are effective social service methods currently in use which could be expanded to a broader application. The Housing First model provides barrier-free, rapid placement to permanent housing combined with service provision for homeless adults and people with disabilities. The service provision involves a contemporary recovery philosophy, centered on the blended theoretical approaches of Harm Reduction and Motivational Interviewing. Housing placement is offered based on a triage system using a vulnerability index to assess mortality risk and is not conditional on service provider treatment goal perquisites, such as abstinence from substance use. This entry reviews the academic peer reviewed literature with a specific focus on the evidence from randomized controlled trials of the Housing First model to assess its ability to provide housing stability (primary function) and its cost-effectiveness (feasibility). Twenty peer-reviewed journal articles based on randomized controlled trials are reviewed in this entry. Each of the 20 articles reported the finding of increased housing stability from the randomized controlled trial or a subgroup of the randomized controlled trial. Four of the 20 articles also had cost-effectiveness as an outcome, and all four showed significant cost-effectiveness of the Housing First model compared with treatment as usual.