Peer relations contribute substantially to both social and cognitive development. The essentials of friendship are reciprocity and commitment between individuals who see themselves more or less as equals. Affiliation and common interests, the main themes in friendship relations, are first understood in early childhood. Friends serve as emotional resources, affording children the security to strike out into new territory and acting as buffers from negative events. Friends also act as cognitive resources, for they teach each other through peer tutoring, cooperative learning, peer collaboration, and peer modeling. Because cooperation and conflict occur more readily in friendships than in other social contexts, friendships are also important to the development of social skills, and children's friendships are thought to be templates for subsequent relationships. Although relatively few investigators have sought to verify the developmental significance of friendship, emerging evidence suggests that having friends, making friends, and keeping friends forecast good developmental outcomes. These outcomes may appear in the areas of positive self-attitudes and the functioning of future relationships. Children with friends are better off than children without friends, though if necessary, other relationships can be substituted for friendships. Consequently, friendships should be viewed as developmental advantages, rather than developmental necessities, and evidence concerning friendships as educational contexts should be read in this light. (AC)