The goal of this Handbook is to provide EU practitioners, in particular prosecutors and police authorities, with an overview of EU and international legislation applicable to CBRN (Chemical, Biological, Radiological and Nuclear) substances and Explosives and with a description of supranational entities, systems and databases active in the field of CBRN-E in support of investigations and prosecutions of transnational crimes involving the use of Chemical, Biological, Radiological and Nuclear substances and Explosives (CBRN-E).