The proportion of injection drug users (IDUs) testing positive for Human Immunodeficiency Virus (HIV) in British Columbia has increased from 3 to 7% since January 1993 (Patrick et al., 1997). We conducted a qualitative study as a first step in a case control investigation aimed at identifying risk factors associated with HIV seroconversion. Sixteen subjects participated in in-depth interviews which were transcribed and analysed using grounded theory methods. Three dominant themes emerged: Addiction, Prevention, and Social Determinants. The results suggest that prevention efforts such as the availability of clean needles and condoms are not adequate to combat the complex social determinants of addiction--be they causal or consequential--which in turn contribute to unsafe injection practices.