This article considers the emergence of specialized Drug Dependence Units (DDUs) to treat heroin addiction in 1968. Disease-based notions of addiction had long coexisted with more 'social' understandings of the condition; those that stressed the social problems resulting from habitual drug use. Although elements of both approaches were to be found in the 'British System' of heroin addiction treatment and control prior to this period, 'social' and 'medical' aspects of addiction were conflated by the Brain Committee which described addiction as a 'social disease' in 1965. This was the result of changes in the population of addicts but was rooted in broader shirts in the perception and location of disease. Tensions, however, still existed between 'social' and 'medical' approaches to heroin addiction and these can be observed in the debates surrounding the establishment of DDUs. Negotiations with hospitals asked to open DDUs were protracted because there was little agreement about what the purpose of these units should be. Experts could not decide whether clinics should stress the treatment of addicts or the control of their behaviour. The Ministry of Health decided to adopt a policy that aimed to do both, thus confirming the bond between the social and the medical. This had significant implications for the future treatment of heroin addiction.