The association between having a reputation for valuing popularity and relational aggression was assessed in a sample of 126 female children and adolescents (mean age=12.43 years) at a 54-day residential summer camp for girls. Having a reputation for valuing popularity was positively related to relational aggression. This association was moderated by both popularity and physiological reactivity to social exclusion (i.e., respiratory sinus arrhythmia reactivity [RSAR] and heart rate reactivity [HRR]). Popular girls with a reputation for valuing popularity were at greater risk for engaging in relational aggression when they also exhibited blunted reactivity to social exclusion. Conversely, girls who had a reputation for valuing popularity but were not popular (i.e., the "wannabes") were at risk for engaging in relational aggression when they exhibited heightened reactivity to exclusion. (Contains 3 figures and 3 tables.)