This chapter discusses research into communication in childhood and adolescence in the context of work on group dynamics. It outlines the ways in which a better understanding of processes of communication can inform work in the area. Communication can be a useful diagnostic tool to understand how children and adolescents play out their group knowledge in everyday contexts. Research into the influence of gender and, to a lesser extent, ethnicity on children's and adolescents’ processes of communication highlights the sometimes profound effect of group memberships on the social dynamics of interaction. Communication in friendship groups may reinforce identification and ingroup norms. Friendship groups provide an opportunity for learning and rehearsing in-group norms of communication, while simultaneously limiting exposure to out-group norms. This has important implications for social developmental theory because communication within friendship groups therefore serves as a reinforcer of intergroup dynamics.