This study examined how the manifestation of overt aggression changes during early adolescence using Hierarchical Linear Modeling. The distinct courses of physical and verbal aggression identified in this study provide support for developmental transformations in overt aggression, which would have been obscured unless aggression had been defined with greater specificity. The examination of gender effects revealed that while boys demonstrate higher initial levels of physical and verbal aggression, there were no gender differences in the growth of physical and verbal aggression. In addition, the testing of ethnicity effects demonstrated that Blacks and Hispanics show higher initial levels of physical and verbal aggression than Whites, however, adolescents from other ethnicities did not differ from Whites in terms of initial aggression levels. Despite the significant differences in initial status, ethnicity did not significantly predict the growth of aggression with the exception that Blacks exhibited a faster rate of decline in physical aggression. The limitations of this study and the implications for future research and practice are discussed. (Contains 3 tables.)