Drug addiction treatment is increasingly complex. Only 5% of prisons and 34% of jails offer any detoxification services, and only 1% of jails offer methadone for opioid withdrawal. Even fewer facilities offer medication assisted therapy (MAT) for alcohol or substance use disorders despite the tremendous evidence base supporting the use of medications to treat addiction. Untreated opioid dependence both within corrections and in the community is associated with HIV, Hepatitis C, crime, and death by overdose. Substantial evidence argues that these risks are reduced through long-term treatment with agonist medications such as methadone and buprenorphine. Only a minority of prisoners receive any addiction treatment while incarcerated. Those that do are usually offered behavioral interventions, which when used alone have extremely poor outcomes. Although there are limited studies on the outcomes of drug treatment during incarceration, there are nearly 50 years of evidence documenting the efficacy of methadone given in the community in reducing opioid use, drug-related health complications, overdose, death, criminal activity, and recidivism. Buprenorphine is similarly an effective, safe, and cost-effective long-term treatment for opioid dependence that reduces other opioid use and improves health and quality of life outcomes. There is a growing role for MAT in jails, and to a lesser degree in prisons for the treatment of alcohol and opiate dependence. This chapter presents the current state of evidence based practice in correctional MAT models.