Drug law enforcement and treatment are often considered as alternative approaches to dealing with the problem of illicit drugs. This bulletin argues that both approaches have a role to play in minimising the harm associated with heroin use. The bulletin discusses the effects of drug law enforcement on the monetary and non-monetary costs of heroin and the role of these effects in deterring heroin use. Evidence is presented showing that drug law enforcement can encourage heroin users into treatment, thereby reducing some of the harm associated with heroin use. However, there is also evidence that drug law enforcement can have unintended consequences which increase other harms associated with heroin use. The bulletin concludes with a discussion of implications for policy and further research.