This chapter outlines the policy background for the care of the seriously mentally ill in the United States, and examines the definitions and practices of case management and its variants. For individual patients, case management has been defined as the coordination of care for patients who require a multiplicity of services. The many variations in the practice of case management share a common set of underlying principles. Their starting point is that vulnerable patients with long-term psychiatric disorders need therapeutic interventions which optimise their social adjustment and minimise their functional disabilities. Community Support Treatment and Rehabilitation (COSTAR) is a community mobile treatment team, closely modelled on Program for Assertive Community Treatment (PACT), which combines case management and psychiatric treatment for a group of long-term mentally ill patients who are unable to utilise effectively the traditional outpatient mental health service system.