This study reports the results of an experiment comparing a developmental-acquisition model of case management to usual case management services provided through a mental health center. This is the first study of case management with the chronically mentally ill to employ a true experimental design comparing two types of case management service. The statistically significant discriminant functions resulting from the analysis correctly classified 77% of the subjects based on the case manager's assessment of clients' socialization skills, assessment of community living skills by a significant other and the client, the client's tolerance of stress, use of leisure time, community behavior, and vocational training. Implications for research and service delivery are discussed.