Although there is a theoretical and empirical basis for age-related changes in adolescents' empathy and prosocial behaviors, as well as in bidirectional relationships, research examining their codevelopment is lacking. Specifically, research on the extent to which an adolescent's mean-level growth in empathy is related to parallel mean-level growth in his or her prosocial behavior is needed. This 3-year longitudinal multicohort study of adolescents (