The present study was designed to assess both the prevalence and structure of antisocial behavior in a normative sample of preschoolers. Prevalence estimates suggested that 40% of preschoolers exhibit at least one antisocial behavior each day. Furthermore, 10% of preschoolers exhibit six or more antisocial behaviors each day. Consistent with research based on older children, factor analyses provided support for conceptualizing antisocial behavior in early childhood as consisting of both overt and covert dimensions. While both overt and covert behaviors had acceptable test-retest reliability, only overt behaviors had acceptable interrater reliability. Finally both overt and covert dimensions of antisocial behavior were uniquely related to general measures of conduct problems, hyperactivity, and adult and peer conflict in the classroom setting. Findings are discussed with regard to early assessment and the developmental course of antisocial behavior.