Early adolescent girls and boys (N = 33) with known histories of relational aggression and/or victimization gave detailed accounts of the nature, frequency, intensity, course, and impact of relational aggression among their peers. They also described reasons for, and forms of, aggression after being prompted by a series of hypothetical vignettes. Despite identifying many forms of aggression that were similar for girls and boys, some sex differences were found; girls were described as experiencing more victimization within close friendships than boys, with a focus on maintaining exclusivity. Boys described exclusion from larger groups with themes of masculinity, athletic skill, and/or perceived sexual identity. Girls' and boys' perceptions about the motivations for these different forms of relational aggression were quite similar. These included power, popularity, and wanting to fit in as well as the aggressors' emotional states and the victims' characteristics. (Contains 2 tables.)