In this study, questions regarding the prevalence of mutual antipathies and their relation to the behavior of individual children were examined among preadolescents and adolescents. Mutual antipathies were defined as relationships in which children mutually nominated one another as least liked on a sociometric task. A distinction was drawn between same sex (SS) and mixed-sexed (MS) antipathies. Findings indicated that SS antipathies were more prevalent among boys than girls, especially in preadolescence. Involvement in MS antipathy was similar among boys and girls in preadolescence and adolescence. Involvement in SS antipathies was related to greater antisocial behavior and greater aggressiveness in preadolescence and adolescence, after social rejection was taken into account. Involvement in MS antipathy was associated with different patterns of adaptation for boys and girls: boys with MS antipathies were more antisocial and more prosocial in preadolescence, and more aggressive, higher achieving, and less withdrawn in adolescence, whereas the opposite pattern was observed for girls with MS antipathies. (EV)