The guidance provided is based on an analysis of how successful programs have been designed, implemented, and operated in communities across the United States. Ideas are offered regarding developing, implementing, financing, and sustaining programs that integrate the mental health, substance abuse treatment, and justice systems for adult and youth populations with co-occurring disorders. It reports successes, but does not provide a precise step-by-step approach. It offers principles and perspectives with which to interpret local conditions and identify promising directions. The communities whose programs have been effective have found ways to develop new linkages among mental health, substance abuse, and criminal justice systems. Program innovations reflect an investment in the concept of system integration, under which all three systems recognize the need for a holistic approach for treating each person; they are willing to share information, money, and clients across the three systems. Suggestions for building successful collaborations focus on the start-up stage and implementation. Other sections focus on program financing and strategies for sustaining successful programs. Appended program descriptions and resources and 10 references