Assertive community treatment (ACT) is a widely-used intervention for the most severely impaired persons with mental illness. Because it differs from traditional treatment approaches in its philosophy, its organization, and in the clients it serves, financing strategies that are appropriate for standard services may not be optimal for ACT. In developing new payment systems, policymakers must choose between targeted strategies that attempt to influence the treatment process directly and those that establish broad goals for effectiveness, access, and efficiency while allowing providers more latitude in the treatment process. These choices profoundly influence how and to whom ACT is available.