The homelessness, drug and alcohol, and mental health service systems are separate service structures in Australia. They have their own unique funding and governance arrangements and work in separate domains. The homelessness service system fits largely within a community services support framework, while drug and alcohol, and mental health services are embedded within their respective health systems. 

Despite the fact that the homelessness, drug and alcohol, and mental health service systems are separate, they share many of the same clients and address similar problems among clients. Homelessness services, for example, provide support to clients who also have drug and alcohol, and mental health needs. Therefore, the homelessness, drug and alcohol, and mental health service systems interact. Service integration and effective working relationships between services across the homelessness, drug and alcohol, and mental health systems is, a priori, critical in achieving good outcomes for clients wherever they may be located. 

Service integration has become a point of policy focus in recent years. Despite the focus on systems and service integration in the present policy environment and among practitioners, there has been no study, as far as we are aware, of the integration of homelessness, drug and alcohol, and mental health services in Australia that also considers the perspective of clients. 

This study aims to fill this critical gap in the literature. The purpose of the present study is to increase our understanding of the extent and ways in which homelessness, drug and alcohol, and mental health services are working together to provide services to clients with particular emphasis on the needs of homeless people. The study also considers the barriers, costs and benefits of service integration and the perceived effectiveness of various integrated service delivery responses. It focuses at both the service level and at the level of the client and addresses the question as to client perceptions of the integration of services and the effectiveness of the services they are receiving.