Abstract: National drugs observatories have flourished and developed rapidly over the last two decades as a direct consequence of the decisions taken to establish regional drug monitoring systems, both in the European Union and in the Americas. Initially, there was no reference framework available — observatories were set-up using trial and error, taking into account different national contexts and resources. This explains why today there are as many models of observatories as there are countries establishing them. Looking back at this long process, there seemed to be a need to formalise the experiences in the field, and to identify some key concepts and principles that remain valid irrespective of country or region. This handbook, a joint production by the European Monitoring Centre for Drugs and Drug Addiction (EMCDDA) and the Inter-American Drug Abuse Control Commission of the Organization of American States (CICAD–OAS), presents and describes in a clear and informative way the core operational processes and the key strategic factors that are common to all national drugs observatories.