This article investigates the role of interpersonal relationships in shaping sex differences in the manifestation, etiology, and developmental course of conduct problems and their treatment needs. The review examines whether: (1) Girls' conduct problems are more likely than boys' to manifest as a function of disrupted relationships with caretakers and peers; (2) For girls more than for boys, the outcomes of conduct problems in adolescence and adulthood, and related treatment needs, are more likely to be a consequence of the quality of interpersonal relationships with others, particularly opposite-sex peers and partners. Evidence reviewed suggests that boys and girls share many similarities in their expression of conduct problems, but that a relational perspective does unify important differences. There is fair evidence that girls with conduct problems are more likely to come to the attention of authorities because of chaotic, unstable family relationships, and to express antisocial behavior in the context of close relationships; there is stronger evidence that the course and outcomes of conduct problems in females versus males pertain to interpersonal relationship impairments. Those sex differences map onto specific differences in treatment needs. Further empirical testing of the proposed relational model is indicated.