In response to increases in Illinois prison population, low rates of access to substance abuse treatment services while in prison, and high rates of recidivism, on January 2, 2004, the Illinois Department of Corrections opened the Sheridan Correctional Center as a fully-dedicated, modified therapeutic community for incarcerated adult male inmates. Since the program began, a process and impact evaluation has been conducted by researchers from Loyola University Chicago, the Illinois Department of Corrections, the Illinois Criminal Justice Information Authority, Treatment Alternatives for Safe Communities (TASC), the Safer Foundation, and WestCare. After 6 � years of operation, covering the period from January 2, 2004 through the week of end of State Fiscal Year 2010 (June 30, 2010).