This study examined the long-term effectiveness of the ACCESS (Access to Community Care and Effective Services and Supports) project on service utilization and continuity of care among homeless persons with serious mental illness. A 3-year longitudinal analysis, using Medicaid claims data, tracked behavioral health service utilization among 146 Medicaid-eligible participants in the Pennsylvania ACCESS program. Utilization patterns of inpatient, outpatient, and emergency department services for psychiatric and substance abuse treatment were examined during the year prior to, during, and one year after the implementation of the ACCESS project. Use of psychiatric ambulatory care significantly increased among intervention participants and remained greater following ACCESS intervention. Better continuity of care following hospitalization was achieved during and after the intervention. The number of days spent hospitalized significantly decreased during the intervention. These results suggest that the ACCESS intervention was effective in linking hard-to-reach homeless persons with serious mental illness to the community mental health service system, and that this effect was maintained after termination of the intervention.