"Prisoners experience high rates of drug dependence, health problems and premature mortality. Without intervention, they often come into further contact with the criminal justice system, creating further health risk. Opioid dependence is common among prisoners, yet treatment with opioid substitution therapy (OST) may reduce or prevent morbidity, mortality and offending … The results highlight that the prison setting provides an important opportunity to engage people in OST. Notably, OST treatment in prison and immediately post-release was found to be highly protective against mortality both while incarcerated and after release. Considering some of the known benefits of OST, this study provides strong evidence to support the value of OST programs within the criminal justice system" (p. 1). Results are provided for: the natural history of criminal justice system involvement among opioid-dependent people, 1993–2011; the extent of imprisonment of opioid-dependent people, 2000–12; potential differences in the impacts of buprenorphine and methadone on treatment retention and mortality; gender differences in opioid substitution therapy engagement; The association between retention in opioid substitution therapy and crime among opioid-dependent people; the impact of opioid substitution therapy provision in prison upon in-prison mortality; the impact of opioid substitution therapy on mortality following release from prison; and cost effectiveness of opioid substitution therapy in reducing mortality post-release among this group.