Background: While much has been written about the positive individual and collective effects of Supervised injection services (SIS), notably on health and drug-related harm, little research focuses on their operational context and constraints. Building on Lascoumes and Le Gales's "public policy instrument and instrumentation " framework (2007), this article analyzes the implementation of Montreal SIS and discusses how the organizational aspects of SIS produce the contexts for drug injection. Methods: Using an ethnographic approach, this article draws on three types of data: 10 months of participant observation in a SIS (700 h); 19 semi-structured interviews with staff members (social workers, peers, heads of staff, management); and analysis of organizational documents (protocols, staff notebooks).Results: First, this article examines how political context and advocacy coalitions produced Montreal SIS as a public policy instrument, affecting both the philosophy and the implementation of the service. It shows that Montreal SIS were developed under a health care network blueprint rather than a community organization harm reduction framework. Then, it analyzes how SIS as a policy instrument defines what constitutes appropriate injection practices, trying to supervise injection as an individual and technical act, rather than a broader social practice composed of pleasure, rituals, routines, and group dynamics.Conclusion: Montreal SIS were conceptualized under a "health banner " and through alliances between regional public health administration and local well-known community organizations. They were then developed mostly under a health care administration blueprint, although operated at a ground-level by local community organizations. It created tensions between the logics of "zero risk " and "harm reduction ", and ambiguity about how injection should be supervised and what parts of drug use could be managed.
