An account is provided of the Early Warning System on ‘New Psychoactive Substances’ in operation in the European Union. Technical and subsidiary material is placed in 20 Appendices, which list controlled substances and cover topics such as: precursor chemicals, related legislation, sentencing guidelines and detailed chemical/pharmacological profiles of the most commonly-abused drugs. There is a glossary and a bibliography, while extensive footnotes support the text and provide references to selected publications and Internet sources.