Introduction and Aims. To examine age-related differences in drug use and risk among regular injecting drug users (IDU) in Australia. Design and Methods. Cross-sectional data from the 2006 Illicit Drug Reporting System were examined for age-related differences in demographic characteristics, drug use history and current use patterns and self-reported risk behaviours. Results. IDU under 25 years of age were more likely to have initiated injecting at a younger age, to identify as Aboriginal and/or Torres Strait Islander, and to be injecting daily or more often than their older counterparts. They reported more frequent heroin use in the preceding 6 months, and were more likely to report morphine as the first drug injected than were IDU aged 35 years or over. Younger IDU were also more likely to report providing used needles to others, engaging in recent property crime and drug dealing and arrest in the last year. Conclusions. Younger IDU reported significantly different drug use patterns and higher rates of risk behaviours than their older counterparts. Treatment services need to ensure that harm and demand reduction services deliver messages to new cohorts of IDU, particularly given that their drug use patterns may be different to those of older users.