In the first study, 122 seventh-grade and eighth-grade girls from 2 public suburban schools in a northeastern town provided self-reports of aggression based on 10 items from a measure designed by McDonald et al. (2000). To assess participants' beliefs about the acceptability of relational aggression in addition to other forms of aggression, the study adapted Huesmann and Guerra's (1997) Normative Beliefs About Aggression Scale. In the second study, 1,208 male and female fifth and sixth graders from 4 areas of the country were assessed for their normative beliefs about aggression and self-reported aggressive behavior by using the same instruments as in the first study. Participants completed questionnaires in the fall of 2002. The first study found initial evidence from a principal-components factor analysis that relational aggression and physical aggression are relatively distinct constructs. The second study sought to replicate and extend these findings by conducting a confirmatory factor analysis by using AMOS 4.0 on the 10 aggression items. The findings showed that adolescents who believed aggression (relational and physical) was an appropriate response reported more aggressive behavior compared with those adolescents who believed that aggression was not an acceptable response. Further, these relationships between aggressive beliefs and behavior were specific to the type of aggression being assessed (relational or physical). These study findings have potentially important implications for prevention and intervention efforts that target aggression. 9 tables and 49 references