Outside of Africa, an estimated two-thirds of new Human Immunodeficiency virus (HIV), infections are believed to occur among people who inject illicit drugs. While an urgent need exists for tailored interventions to address HIV risk behaviour within vulnerable groups such as adult injection drug users (IDU), there are major knowledge gaps that must first be addressed if interventions are to be successful. Innovative approaches to examine how participation in particular social contexts and environments foster vulnerability to HIV are crucial to the development of effective intervention strategies among highly vulnerable populations of IDUs. William Small is conducting research to address this need using ethnographic methods to develop empirical information regarding transitions into particular high-risk social contexts, including drug markets and sex trade activities. Specifically, his research focuses on the risk environments in two different geographical settings, Vancouver, Canada and Sydney, Australia. The results will provide critical insight regarding how participation in these high-risk settings influences HIV risks as well as an individual's ability to engage in risk reduction in the context of injection drug use. The information will be integrated with findings from ongoing epidemiological studies in the same locales to test socially-oriented hypotheses regarding the relationship between HIV vulnerabilities and particular social contexts. Ultimately, the findings from Mr. Smalls’ research will help advance the study of HIV risks among IDUs, and inform the development of social and community interventions designed to reduce HIV transmission.