The prescription of heroin to dependent users has been a distinctive feature of British drug policy for almost a century now, and in recent years the policy’s evidence-base has grown significantly. However, while the evidence for heroin assisted treatment’s effectiveness is strong it is somewhat limited by the clinical setting of the randomized control trial and thus leaves a number of important areas unexplored. This article investigates some of these through a sociological lens informed by both developments in regulatory theory and ethnographic research with a heroin-using population in north-west England. It is argued that heroin prescription has currently ‘untapped potential’ as a means of regulating heroin markets, but also that it presents a number of ‘unanswered questions’ regarding heroin’s socio-economic roles in marginalized communities and the importance of heroin-using identities.