In this study, the authors explored the link between deviant youth group (DYG) membership and antisocial behavior through a large student survey conducted by means of the same questionnaire in 62 cities in 30 countries. The sample (N = 40,678) was made up of 7th-, 8th-, and 9th-grade students, both boys and girls, attending different types of schools. The definition of DYG that the authors used was the one drawn up by the Eurogang network: "Any durable, street-oriented youth group whose own identity includes involvement in illegal activity." About 4.4 percent of youths were considered as DYG members according to this definition, with prevalence rates differing markedly among different countries, from less than 1 percent to more than 16 percent. In general, DYG membership implied a higher prevalence of delinquency, violence, and alcohol and drug use. Differences between DYG members and nonmembers were greater with regard to more serious antisocial behavior. Although the prevalence of DYG membership varies in different countries, the association between DYG membership and antisocial behavior is quite similar in the different national contexts. (Published Abstract)