This essay traces a brief genealogy of state-funded drug ethnography and its relationship to public health projects such as HIV prevention. Ethnographic research on drug use was a critical part of making invisible practices visible in ways that rendered them amenable to intervention. The essay goes on to describe how harm-reduction norms were promulgated through the bottom-up tactics of health-oriented social movements, and simultaneously administered through an institutionalized and even standardized set of beliefs issuing from the highest reaches of the public health apparatus. Harm reduction is a pragmatic movement to change the personal practices of drug users through “modest interventions” aimed at reducing the risk of HIV transmission though contaminated injection equipment. The essay draws on ethnographic research with injection drug users to discuss how drug researchers represent the social norms associated with harm reduction. We demonstrate how injection drug users take on the language and ethical stances of those who study them, in an effort to construct themselves as ethical subjects. The construction and elaboration of a harm-reduction model in and through grassroots mobilization and public health research is an example of the governance of populations through epidemiological constructions of risk transformed into ethical–behavioral injunctions. Their work has changed the nature of ethnographic encounters between drug researchers and injection drug users (IDUs), who are subject to the incitement to discourse constructed by harm-reduction norms and practices as they participate in ethnographic research.