The SurvUDI/I-Track network focuses on the epidemiological surveillance of HIV and HCV infections among people who inject drugs (PWID) in Quebec. Between 1995 and 2005, 9,596 participants completed 16,111 questionnaires and provided saliva samples. The majority were recruited from community organizations providing services to drug users and are cocaine users. The prevalence of HIV is 14.7% [95% CI = 13.9–15.5], while that of HCV is 63.8% [95% CI = 61.7–65.9]. The proportion of those reporting having injected with syringes previously used by others in the six months prior to the interview has decreased in Quebec City, Montreal, and Ottawa (p-values <0.01, Mantel-Haenszel trend chi-square). The HIV incidence rate declined until 2001–2002 but now appears to be rising again. Both viruses are firmly established throughout the monitored territory. Greater efforts will be required to control these two epidemics. (R.A.)