We consider gender and ethnic differences in the co-occurrence of adolescent behaviors related to health and well-being.Using a nationally representative sample of adolescents in the National Longitudinal Survey of Youth (1997-2000), we examine behavior among students as well as school drop-outs. We use latent class models (LCMs) to identify subpopulations of adolescents with similar patterns of co-occurring behaviors. The generalizability of the findings for African American adolescents in the 1970s is considered using a sample of inner-city youth from the Pathways to Adulthood Survey.For all ethnic groups, we find a subpopulation with 'problem behavior' characteristics (in which early sexual initiation, alcohol use, smoking, marijuana use, and truancy are all highly prevalent). This cluster is most common among European American adolescents and among young men. A subpopulation characterized by behaviors often leading to poor social outcomes (e.g. truancy, early sexual initiation and fighting) is most common for African American adolescents, especially young African American men.Our findings suggest that multi-factorial interventions which address the interrelationships between all of the behaviors are relevant regardless of gender or ethnicity. However, the ethnic and gender differences in the likelihood of specific patterns of interrelationships highlight the importance of considering the ethnic and gender composition of a population when developing future research and interventions.