This article describes the social organization of knowledge production in the formative moments of the substance abuse research enterprise. It describes the institutional arrangements and material conditions of a U.S. Public Health Service laboratory that was housed in a facility run jointly with the federal Bureau of Prisons. The Addiction Research Center (ARC) in Lexington, Kentucky, was dedicated to elucidating the basic underlying mechanisms of drug addiction. The ARC was housed on the rural campus of a prison-hospital called “Narco,” one of two “narcotics farms” in Lexington, Kentucky, and Fort Worth, Texas. For its studies on drug effects, the ARC had access to a pool of drug-experienced human subjects drawn from the ranks of convicted felons. Given their unparalleled access to human subjects, the scientists who worked at the ARC made conceptual contributions still acknowledged today. Based on archival work as well as dozens of oral history interviews with individuals who began their research careers at Lexington, the article presents an analytic, intellectual history of the early work of Abraham Wikler, whose lifelong pursuit of the underlying mechanisms of opiate addiction led him to hypothesize the role of conditioning in relapse, as an exemplar of the kind of scientific research that depended on closely listening to and observing “post-addicts,” as subject participants were called. © 2006 Wiley Periodicals, Inc.