In the therapeutic community (TC), peers are the primary change agents. In their varied social roles and interpersonal relationships, residents are the mediators of the socialization and therapeutic process. This chapter details how peer roles and relationships are utilized by the community to facilitate the goals of socialization and psychological change. The socialization history of serious substance abusers is marked by negative peer influences. Functional roles in the TC are those involving performance demands, prescribed skills and attitudes, and defined relationships with others. Three prominent community member roles are peers as managers, as siblings, and as role models. A defining element of the TC model is the use of peer roles for social learning. The chapter describes how the various community and functional roles in the social organizations are utilized by peers to change themselves and others and how socially conditioned race-ethnic and gender roles and issues are addressed.