To monitor the dynamics of the hepatitis C epidemic among people who use drugs (PWUD) in France, the ANRS-Coquelicot survey was conducted in France between 2004 and 2007. This survey, carried out in five cities (Lille, Strasbourg, Paris, Bordeaux, Marseille), consists of both an epidemiological and a socio-anthropological component. The target population for this survey is both difficult to define and to reach, due to diverse social profiles and relationships with drug use, as well as the stigma associated with drug use. The population of IDUs studied consists of those who frequent specialized services and represents a subpopulation with a “problematic relationship with drugs” and who are generally in socially precarious situations. The methodology used in the epidemiological component employed a random sampling strategy via a survey design, incorporating the Generalized Weight Sharing Method (GWSM), and relies on biological data collection to estimate the prevalence of hepatitis C. The use of innovative methodological tools employed for the first time in France (survey design with GWSM, biological tests) in the ANRS-Coquelicot survey made it possible to produce valid estimates of HCV prevalence in the IDU population, a particularly high prevalence amounting to 60%. The methodology implemented in this survey allowed for the extrapolation of its results to the target population under study. Epidemiology made it possible to describe, measure, and, to a certain extent, generalize the findings. Qualitative data (interviews and ethnographic observations) were compared with the data produced by the epidemiological analysis and provided a better understanding of the social context of the risk and the meaning that people who use drugs attribute to it. The use of both quantitative and qualitative methodologies thus made it possible to address the issue of exposure to the risk of hepatitis C among people who use drugs in all its complexity. (Publisher’s presentation)