Despite research demonstrating that approximately 5% of study populations are composed of severely antisocial persons who account for a disproportionate share of problem behaviors, there have been no nationally representative studies assessing this phenomenon among adolescents. Using a large nationally representative sample (N = 18,614), we identified a severe group (4.7% of respondents) characterized by involvement in varied and intensive externalizing behaviors, greater internalizing, lower academic achievement, and less parental involvement. The current study is the first nationally representative study of criminal careers/externalizing behaviors among adolescents in the United States, which is convergent with prior research and theory.