Prior research addressing children's antisocial and prosocial behaviours have predominantly used a predetermined set of criteria which have been devised by adults. This psychological approach has lead to the perception of children as an individual phenomenon, using a dichotomy of behaviours consistently regardless of their immediate social environment. Therefore an argument is made for the use of an inductive, sociological approach in order to gain understanding of the everyday social interactions which children engage in. Conversation analysis and membership categorization analysis (Sacks, 1992a, 1992b) were employed to transcribe audio and video footage taken of thirteen, four-year-old children in their primary school playground in mid-Wales. The detailed and iterative analysis found that children employ specific resources to organise the social order of their playground. These resources include the use of name calling; access tools; possessive pronouns and collective proterms; reference to gender; physical gestures and the use of playground huts. The resources were used in the interaction of excluding or affiliating with peers, and also in the disaffiliation of peers where no further interaction was produced. These actions worked to produce different outcomes but were often used simultaneously in the co-construction of context. The wider findings which emanated from the detailed analysis identified the issues of sequences in children's establishment of social order; the context free and context sensitive nature of affiliation, disaffiliation and exclusion; issues of power; verbal actions supported by physical gestures; children's use of their environment; exclusive dyads; and children's social competence. The thesis holds implications for practice where practitioners can acknowledge the complex, multidimensional aspects of children's social organisation processes in order to avoid stereotyping. This study extends research which uses conversation and membership categorization analysis in the area of childhood studies which is important as this methodology affords unique access into children's worlds.