BACKGROUND AND AIMS: Current injecting drug users (IDU) in major street drug markets within greater Melbourne were recruited to a longitudinal study on blood borne viruses. Here we investigated risk factors for hepatitis C virus (HCV), hepatitis B virus (HBV) and HIV infection in these IDU at the time of their recruitment. METHODS: Three hundred and eighty-two IDU completed detailed questionnaires on their drug use and risk behaviours, and provided blood samples for serology testing. These data were analysed using univariate and multivariate techniques. RESULTS: The overall prevalence of exposure to HCV, HBV and HIV was estimated at 70%, 34% and <1%, respectively. Independent predictors of HCV exposure were history of imprisonment (RR 1.34, 95% CI 1.19-1.52), use of someone else’s needle or syringe (RR 1.23, 95% CI 1.07-1.42), >7.6years length of time injecting (RR 1.21, 95% CI 1.07-1.37), and originating from Vietnam (RR 1.12, 95% CI 1.07-1.18). Independent predictors of HBV exposure were HCV exposure (RR 2.15, 95% CI 1.35-3.43), >7.6years length of time injecting (RR 1.57, 95% CI 1.17-2.13) and originating from outside Australia (RR 1.60, 95% CI 1.22-2.10). Neither prison- nor community-applied tattoos predicted HCV or HBV exposure. Up to 31% of IDU who injected for 1year or less were HCV antibody positive, as were 53% of those who injected for 2years or less. CONCLUSIONS: Ongoing engagement with young IDU, through the provision of harm reduction education and resources, is critical if we are to address blood borne viral infections and other health and social harms associated with injecting drug use.