Peers have both positive and negative influences on children; therefore, considerable attention has focused on assessing peer relationships and friendships through childhood and adolescence. The present article provides an overview of the main methods of assessing peer relationships. The adaptive nature of children's peer relations has been assessed through four main methodologies: (1) asking the children themselves about elements of peer relations and friendships; (2) asking children about their perceptions of others within the peer group; (3) asking adults (i.e. parents and teachers) about the peer relations skills of children in their care; and (4) directly observing children during interactions with peers. Each of these approaches is described, with attention to relative strengths and weaknesses and their suitability for assessing peer relations in early childhood, middle childhood, and adolescence.