The results of this study contribute to the literature which is beginning to delineate the importance of social identity processes during development. The participants in the study reported a high level of identification with their friendship groups, and this identification was related to each of the outcome measures. The results revealed a clear relationship between social identification and self-concept such that those adolescents who were highly identified with a group of friends reported higher levels of self-esteem overall than did those less identified with a group. For understanding of adolescents’ self-evaluation processes, the finding that group identification predicted domain-specific self-esteem raises an interesting issue concerning social identity theory’s assumptions about the self-concept. In summary, the study highlights the role of friendship group identification in self-concept and social development, and further confirms the importance of group membership in adolescence. Prior research has argued that friendship groups make a unique contribution to development during adolescence by serving as an important reference point for the evaluations of self and others. This study applied a social identity perspective to the study of adolescent self-concept and social development. The British study consisted of 114 students ages 14 to 15 years. Appendix and references