Studies have found that young injection drug users (IDUs) may be at elevated risk for blood-borne infection transmission, however few studies have evaluated risk longitudinally. We compared variables between younger (>or= 29 years) and older (<or= 30 years) IDUs in Vancouver, British Columbia, Canada between 1996 and 2006. Of 1598 participants, 582 (36%) were aged <or= 29 years. In prospective analyses (N = 1598), factors associated with younger age included: borrowing syringes, and frequent (>or= 1 daily) injection of heroin, cocaine, and speedballs. Additionally, younger IDUs were less likely to access drug treatment or methadone maintenance therapy (MMT) and test HIV and HCV-positive. Younger IDUs have lower HIV and HCV prevalence, but a higher risk profile and lower uptake of drug treatment. These factors underscore the need to target this age group and develop youth friendly interventions to minimize drug-related harms.