BACKGROUND: The decision by the UK government to leave the European Union comes at a time when parts of the UK are experiencing a marked rise in reported gun and knife crimes. The health effects of Brexit will have serious consequences as to how the UK tackles this upsurge in drug-related crime. HEALTH POLICY PROCESSES: The UK's future participation with the EU's specialised agencies will depend on the detail of any agreement reached on future collaboration with the EU and its drug agency, the EMCDDA. CONTEXT: The EMCDDA provides the EU and its Member States with a factual overview of European drug problems and a solid evidence base to support debates on drugs policies. It also supports early warning initiatives and coordinates measures at national and supranational levels with Europol and supranational enforcement agencies. EXPECTED OUTCOMES: While these arrangements might continue throughout any transition period, those working within the sector require guidance and assurances from the British government about its long-term intentions after any transition. CONCLUSIONS: The scale of collaboration between the UK and European institutions is extensive. It is not clear how this might be replicated after Brexit. Yet an alternative framework of collaboration between the UK and the EU is clearly needed to facilitate shared and agreed approaches to data sharing and drug surveillance after Brexit.