Objective: To describe patterns of infection with, and risks for, hepatitis A, B and C viruses (HAV, HBV, and HCV) in male adolescents detained in the Melbourne Juvenile Justice Centre (MJJC). Methods: A cross-sectional serosurvey for HAV, HBV, and HCV among 90 male adolescents aged 15-18 years who were resident in MJJC for more than 1 week in 1996. Results: Nine percent had been exposed to HAV, 8% were positive or equivocal for exposure to HBV, and 21% were antibody positive for HCV. All those with hepatitis markers except one positive for HAV had been injection heroin users for more than 1 year. Of those who were not HBcAb positive, only 28% were immune to HBV. For most respondents, sexual and drug-using risks began in the early teens and were associated with leaving school prematurely. Conclusions: Respondents were vulnerable to exposure to blood-borne viruses from an early age, posing a challenge for health education programs. An opportunity exists for harm minimization and prevention of spread of blood-borne viruses within the first year of injection drug use in this population.