The study, called the International Youth Development Study, recruited students in the fifth, seventh, and ninth grades in 2002. Teachers distributed information packets to students, who took them home to parents and then returned the forms over a 2-week period. Only findings from the seventh and ninth grade cohorts are reported in this paper due to greater variation in antisocial behavior. The measures of antisocial behavior, the consequences of this behavior, and the risk and protective factors for antisocial behavior were drawn mostly from the Communities That Care survey. Surveys for the two waves of data collection were administered in late winter in 2002 and 2003. Chi-square analyses were conducted separately for males and females. The rates of antisocial behavior were similar for the two States at both time-points; however, there were some differences in the rates of specific types of antisocial behavior; and there were clear differences between the States in students' experiences of school suspension and arrests, with Washington State students being more likely to receive these consequences than Victorian students. School suspension increased the risk of subsequent antisocial behavior in both States. Antisocial behavior in younger years was predictive of the same behavior 12 months later, suggesting the importance of early intervention when antisocial behavior emerges. Modifying student attitudes toward drugs and related behaviors may also reduce subsequent antisocial behavior. Poor family management and family conflict increased the risk of antisocial behavior. Students' belief in moral values and the ability to control emotions in stressful situations provided protection against antisocial behaviors. 7 tables and 31 references