Latent growth curve analysis was used to examine the structure and interrelations among aggression, drug use, and delinquent behavior during early adolescence. Five waves of data were collected from 667 students at three urban middle schools serving a predominantly African American population, and from a more ethnically diverse sample of 950 students at four rural middle schools. One set of models focused on changes in individual behaviors; the other on changes in a global problem behavior factor. Models with separate growth trajectories for aggression, drug use, and delinquent behavior provided the best fit for both samples and revealed relations between initial levels of aggression and subsequent changes in the other behaviors. Boys and girls differed in their initial levels of these behaviors, but not their patterns of change. Differences in growth curve trajectories were found across samples. These findings have important implications for assessment and prevention of problem behaviors in adolescents.