Injection drug use may result in severe health consequences including increased risk of viral infections such as HIV and hepatitis C, soft tissue infections, and drug overdose. Recently, with increasing attention being paid to the impact of environment on individual and public health, intervention efforts for injection drug users (IDUs) have moved beyond the modification of individual behaviour and focused on modifying the environments in which people use injection drugs. One recent and controversial example of this involves medically supervised injection facilities, where IDUs can inject pre-obtained illicit drugs under the supervision of health care professionals. William Small is studying and comparing three types of injecting settings in the Downtown Eastside: private injecting spaces (such as homes), public injecting spaces (such as alleys), and Vancouver’s supervised injecting facility. He is examining how the social and physical context of each setting influences the ability of injection drug users to employ HIV-prevention measures and safer injection practices. The findings of this research will build important knowledge about the health and HIV vulnerabilities of IDUs in the Downtown Eastside. Also, this research will provide information on the impact of current interventions, which may inform future interventions for addressing injection drug use.