© Health Research and Educational Trust. Objectives To estimate the effects of medical home support on the use of clinical services and Medicaid expenditures. Data Source Medicaid claims. Study Design A difference-in-differences model where changes in utilization and expenditures of the intervention group are compared to changes in the nonintervention group. Extraction Methods Using Medicaid claims from October 2010 through September 2013, service use and expenditures are measured for 12 months before and 21 months after implementation. Changes for four health status groups are examined separately. Principal Findings The introduction of community-based support was associated with a small reduction in use and no statistically significant overall effect on expenditures. However, among those with chronic and/or mental health conditions, there were modest, statistically significant increases in use of and expenditures for a range of ambulatory and inpatient health care services, while service use for those without these conditions declined. Emergency department use increased for all groups. Conclusions Community-based support for medical home practices is associated with a shift in the service mix provided to higher cost, more vulnerable subgroups in Medicaid. Such systems are unlikely to be associated with significant overall cost savings, at least in the short term, but may have other benefits.