To evaluate the effectiveness of an intensive system of case management for high end users of inpatient care in reducing psychiatric inpatient utilization. A prepost study design with a contemporaneous comparison group was employed to determine the effects of a State designed intervention to reduce inpatient care for adults with a mental health disorder who had high utilization of inpatient psychiatric care between 2004 and 2007. Logit and negative binomial regression models were used to determine the likelihood, frequency and total days of inpatient utilization in the post period as a function of the intervention. Data from administrative reporting forms and Medicaid claims were used to construct inpatient utilization histories and characteristics of 176 patients. Patients in both groups had a significant reduction in mean inpatient days. However, being in the intervention program did not result in lower odds of being re-hospitalized or in fewer episodes during the study period.