The document reviews more than 30 years' research on the efficacy of crime prevention and mitigation in reducing illicit drug use and/or the harm it causes, and identifies areas where further research would inform or improve existing policy. It reviews past research on deterrence, highlighting the limited amount known in this area in relation to the effect of sanctions on behavior, the effect of changes in sentencing legislation on court sentencing practice, and the effect of changes in sentencing practice on perceived sentence severity. Further, it discusses research on drug market disruption, highlighting the limited knowledge about the effects and effectiveness of supply-side drug law enforcement. It considers coerced treatment, in part because there is evidence that coerced treatment is at least as effective as voluntary treatment, both in retaining people in treatment and producing beneficial outcomes. Finally, it discusses research into primary prevention. Overall, the book focuses on the effects of law enforcement and the criminal justice system on entry into treatment because it seems that the policy issues in this area have been less extensively researched, even though from the standpoint of crime prevention and mitigation, the report deems them more important. Figures, tables, notes, references