Prior to analysing and comparing delinquent groups of youths at the international level, it is necessary to create a definition of this phenomenon: what is a gang? Definitions of what constitutes a juvenile gang within comparative research are invariably general in nature; and their subsequent operationalisation in empirical research constrains research about gang membership in specific contexts. This article argues that the ‘Eurogang’ definition employed in the second wage of International Self-Report Delinquency (ISRD) Study has a number of potential weaknesses; and this study offers a solution by proposing a revised gang definition for the Czech Republic, Germany, Austria and Switzerland.