Over the past 40 years enormous changes have occurred in the philosophy and management of corrections and these changes had a dramatic impact correctional practice. The “War on Drugs” focused on the philosophies of incapacitation and deterrence. As a result the number of drug involved offenders entering correctional facilities greatly increased. Policy makers, correctional administrators and the public began to realize that many of these offenders had serious drug problems and that onerous punishment and longer prison sentences were not the answers to the drug-involved offenders’ problems. A surprisingly large number of them returned to prison a relatively short time after release to the community. In response to this problem, many jurisdictions initiated drug treatment in correctional facilities so drug-involved inmates could receive treatment while incarcerated. This chapter reviews the research literature to examine whether these programs are effective in reducing the drug use and criminal activities of drug-involved offenders once they return to the community. We found some types of drug treatment programs are effective in reducing recidivism, although the research is disappointingly poor in terms of design quality and there are few randomized controlled trials.