As a specialist in substance dependence issues, the author outlines the fundamentals of prevention strategies (beginning with the question: Are people with substance use disorders capable of seeking prevention services?): understanding the practices of people who use drugs, as well as the contradictory concepts and perceptions held by certain prevention stakeholders regarding them. Drawing on research data from the IREP (Institute for Research in the Epidemiology of Drug Dependence) and abroad, he describes social perceptions of injection drug use through an ethnological lens, with the aim of promoting a prevention message centered on disinfecting syringes with bleach (the Chicago program). The over-the-counter sale of syringes in France since 1987, initially perceived as a source of risk, has in fact reduced syringe sharing, driven by a desire for self-protection. This shift in behavior was confirmed in 1990–91: no syringe sharing, condom use, though with limited knowledge of syringe decontamination methods. The Chicago program’s approach, which aims to empower drug users as active agents in their own prevention, was implemented in the Paris region, Lille, Marseille, and Metz, by reaching out to drug users wherever they gather. The message is: use a new or disinfected syringe; a bottle of disinfectant is distributed for this purpose. An evaluation of the initiative was conducted.