The stability of and dyadic influences on physical aggression in adolescents' dating relationships have implications for understanding the etiology of intimate partner violence and, in turn, prevention efforts. We studied the stability of aggression and tested a longitudinal dyadic model of psychological and physical aggression in samples of adolescent males and females who remained in relationships for 3 months. Physical aggression against dating partners was remarkably stable. Verbal aggression, jealous behavior, and controlling behavior formed a latent construct psychological aggression. Psychological aggression predicted physical aggression both concurrently and longitudinally. Dyadic relations were evident for both psychological and physical aggression, and these dyadic relations highlight the need for prevention and intervention incorporating dyadic issues with young dating couples.