Presented is an interactional analysis of preschool circle time that builds on the view of classrooms as social systems within the broader culture of schooling. In the preschool studied, 18 children, 2 teachers, and several student teachers learned to use circle time together. The head teacher's approach to circle time was a developmental one, which involved the idea that children learn about language in the course of using language. Circle time was obligatory; reflected the demands of large group living; and was not a social organization which children would be likely to construct on their own in the neighborhood. Circle time was introduced to children in the school and would be an element of their experience well into the primary years. The social participation structure for conducting circle time events was uncovered with the use of Green's (1983) conversational mapping system. Findings suggested that the rules, guidelines, expectations, and roles within events changed over time. The focus of learning within events, which was evident in social action rules, shifted from the formation of the circle to the production of collaborative conversation. This shift was interpreted in terms of the children's developing competence in group conversation. Concluding remarks propose a potential peer culture dimension to circle time. (RH)