Substance use disorders are highly prevalent among adults with mental health disorders. In many health service delivery areas, mental health and addictions services are delivered separately. However, current best practices indicate that integration of mental health and addictions services can lead to better outcomes for clients with co-occurring disorders, including fewer hospitalizations. Service integration in the community can occur in many ways, including full or partial program integration. While the delivery of mental health and addictions services must be responsive to the needs of the local community, fully integrated programs have the strongest evidence base for positive client outcomes.