This article explores the nature of teacher expertise in the primary school classroom, drawing on theoretical models of expertise and of teaching expertise. It challenges simplistic models of an "outstanding" or "master" teacher to argue that since teacher expertise is both situated and prototypical, it is manifested in different ways according to context and the individual. The complexity and contingency of the primary school classroom means that the classteacher's expertise must be multi-faceted to enable appropriate responses to events and match between learners' needs and teachers' knowledge. Such expertise is conceptualised in terms of domain, craft and personal/interpersonal knowledge, with the last of these especially important in the primary classroom, and domain not equated with subject knowledge. This leads to a preliminary typology of what distinguishes the primary school classteacher with a high level of expertise. The conclusion considers possible implications for research, emphasising the need for detailed, collaborative empirical work and academic and professional discourse, considering in greater depth the nature of expertise of teachers working with young children, especially in the classroom.