OBJECTIVE:To measure the prevalence and determinants of blood-borne virus (BBV) transmission in ethnic Vietnamese injecting drug users (IDUs). METHODS:The study was conducted in Melbourne, Australia, in 2003. It was a cross-sectional design with participants recruited from street-based illicit drug markets predominately using a snowball technique. One hundred and twenty-seven participants completed a questionnaire that asked about illicit drug use and participants' blood samples were tested for HIV, HCV and HBV. RESULTS:One hundred and three (81.1%) ethnic Vietnamese IDU study participants were HCV positive and three (2.4%) were HIV positive. More than 60% had evidence of being infected with HBV (either in the past, acute infection or chronic infection). Almost 60% had injected daily over the past 12 months. Fifty-nine participants had recently travelled to Vietnam; 24 (41%) had injected drugs in Vietnam; and three (12.5%) reported sharing injecting equipment in Vietnam. CONCLUSION:The prevalence of BBVs was higher in this study's IDU population compared with IDUs in Australia generally, despite the fact that the injecting risk behaviours were similar to IDUs more generally. IMPLICATIONS:Culturally sensitive drug treatment and education programs need to be developed in Australia for both ethnic Vietnamese IDUs and their families to reduce this group's risk of contracting a BBV.