Most studies of injecting drug users (IDUs) have included only urban IDUs; information about rural IDUs is scarce. Recognizing this, the Victorian Injecting Drug Users Cohort Study (VICS) recruited IDUs from rural Victoria as well as Melbourne (population 3.2 million in 1995), capital city of the state of Victoria, Australia. Examination of data collected from IDUs living in Melbourne and the Western District (largest city: Warrnambool, pop. 27 734) revealed numerous differences in behaviour and serology. The primary drug for most Western District IDUs was amphetamines while Melbourne IDUs preferred heroin. Injecting and sharing frequencies were much lower in the rural sample. Hepatitis C antibody prevalence at first test was significantly higher in Melbourne IDUs, although this was clearly related to the difference in primary drugs; conversely, incidence among Western District amphetamine injectors was 16.2 per 100 person-years (py) (during 18.5 py), yet no conversions occurred in metropolitan amphetamine injectors in 29.8 py. Western District IDUs were less educated and more likely to be unemployed and of aboriginal descent than metropolitan IDUs. Variation between populations of Victorian IDUs has implications for the delivery of IDU-related health services; of particular concern is the possibility that hepatitis C has been spreading relatively rapidly among rural IDUs.