Confusion about the cost-effectiveness of case management stems partly from poorly defined assumptions about outcomes and unclear theories of how case management affects costs. The authors discuss how cost-effectiveness is influenced by the characteristics of various case management models, characteristics of the clients served, and contextual factors, including resources available in the treatment system and financial incentives built into various payment mechanisms. Important differences exist between case management models in the mechanisms favored for managing resources, including whether the client or the case manager is primarily responsible for directing the course of treatment, whether reduction in hospitalizations is a primary goal, whether team case management is used, and how the size of caseloads is determined.