The NIMH Strategic Plan seeks novel models and methods for implementing effective mental health services in the community (Strategy 4.1, NIMH, 2008). Related findings by the Institute of Medicine, the President's New Freedom Commission on Mental Health, the Surgeon General, and the National Institutes of Health, as well as a growing body of research describing ineffective community-based mental health services, point to the critical need for strategies to eliminate a variety of barriers to service effectiveness. However, few implementation strategies have been developed to address the broad range of barriers that hinder service outcomes in community mental health agencies and almost no empirical tests of such strategies have been conducted using true experimental designs. As a result, there is much more to learn about strategies that can be used by community-based agencies to improve the way they deliver mental health services. The proposed study will experimentally test the effects of the ARC (for Availability, Responsiveness and Continuity) organizational implementation strategy on the mental health services provided to youth in a sample of 12 community-based mental health agencies in St. Louis, MO. The study will be conducted by the developers of ARC from the University of Tennessee Children's Mental Health Services Research Center (UT CMHSRC) in partnership with the Washington University Center for Mental Health Services Research (WU CMHSR) in St. Louis. The ARC implementation strategy focuses on developing the processes of staff collaboration, participation and improvement-oriented innovation necessary for an organization to implement more effective services by identifying and addressing barriers to effectiveness. Examples of service barriers include problems that plague mental health service systems nationwide, such as the use of ineffective treatment models, staff turnover, client drop-outs from treatment, inefficient referral networks, inaccessible services, and staff resistance to service improvement efforts. We argue that a mental health agency's ongoing capacity to improve the services it provides requires a guided organizational implementation strategy that identifies and addresses such barriers in the organization's social context, service structure and core technology.