In Canada and in many other countries, prisons have become incubators for the transmission of HIV and hepatitis C virus (HCV). Estimates of HIV and HCV prevalence in Canadian prisons are at least 10 and 20 times, respectively, the reported prevalence in the population as a whole--and prevalence rates have been reported to be significantly higher for people who inject drugs. Although people who inject drugs may inject less frequently while incarcerated, the risks of injection drug use are amplified because of the scarcity of sterile syringes and the sharing of injecting equipment in prison. Making sterile injection equipment available to people in prison is an important response to evidence of the risk of HIV and HCV transmission through sharing syringes to inject drugs. In this article, Sandra Chu explains why the government is obligated under international human rights standards and Canadian correctional and constitutional law to provide prison-based needle and syringe programs (PNSPs).