We examined the contribution of relational aggression in adolescents' peer and dating relationships to their psychological and behavioral adjustment. In the Fall and again four months later, 1279 (646 female) grade 9 students reported on relational aggression perpetration and victimization in their romantic and peer relationships, depression/anxiety symptoms (psychological adjustment) and delinquency (behavioral adjustment). Using hierarchical regression analyses, controlling for Time 1 adjustment/behavior, peer relational aggression perpetration predicted depression/anxiety. Dating relational victimization also predicted depression/anxiety, but only for girls. Furthermore, girls who were perpetrators of relational aggression in both peer and dating contexts were most likely to show increases in delinquent behavior. We conclude that dating and peer relationships are not redundant, but make independent and additive contributions to adolescent adjustment. Girls, in particular, may be at greatest risk for poor outcomes when they have relationally aggressive relationships. Results also highlight the need for greater awareness of the complexity and significance of adolescent dating relationships.