The high prevalence of HIV infection and drug dependence among prisoners, combined with the sharing of injecting drug equipment, make prisons a high-risk environment for the transmission of HIV. Ultimately, this contributes to HIV epidemics in the communities to which prisoners return on their release. We reviewed the effectiveness of interventions to reduce injecting drug use risk behaviours and, consequently, HIV transmission in prisons. Many studies reported high levels of injecting drug use in prisons, and HIV transmission has been documented. There is increasing evidence of what prison systems can do to prevent HIV transmission related to injecting drug use. In particular, needle and syringe programmes and opioid substitution therapies have proven effective at reducing HIV risk behaviours in a wide range of prison environments, without resulting in negative consequences for the health of prison staff or prisoners. The introduction of these programmes in countries with an existing or emergent epidemic of HIV infection among injecting drug users is therefore warranted, as part of comprehensive programmes to address HIV in prisons.