This study proposes a new concept of curriculum. The need arises because current notions of ‘curriculum’, as it is used in formal education, distort the nature of practice and education. This is particularly evident in current approaches to education in practical settings, and gives rise to my research question: What is the curricular nature of practice? My answer involves a shift in thinking from seeing curriculum as ‘courses of study’ to ‘courses of action’. In this thesis I move the argument away from that of ‘curriculum for practice’ to ‘curriculum in practice’. In achieving this, my thinking has shifted from ‘curriculum in and as practice’ to ‘curriculum-in-practice’ and then to ‘curriculum-in-( )-practice’, where the hyphens unify notions of curriculum and practice as sides of the same coin, and the empty bracket is filled by the details of practical action and practical reasoning specific to a particular practice domain. The study is in two phases. In Phase 1 I searched social learning and curriculum theories for clues to a curricular understanding of practice. This failed to answer my research question. My way forward was by way of concrete everyday examples of practice and an ethnomethodological understanding of action. In doing this, my understanding of ‘curriculum’ changed from ‘learning planned and guided by some educational institution or programme’ to ‘learning in the here-and-now generated in and as the detail of the practical lived work of particular kinds of action.’ As a contribution to Curriculum Studies, my new concept locates the notion of ‘curriculum’ in practice (of any kind) rather than in schooling (of any form). It avoids adopting a ‘big curricular idea’, emphasises the improvised nature of practical action, focuses on ‘lived work’ rather than ‘lived experience’ and suggests different notions of accountability and rational action. The main implication of this study for curriculum design and development is the suggestion that it should take account of what I call ‘ambient practice’, i.e. the curriculum (the basis for learning) that is generated in any and every action. The main implications for research are to investigate educational experience as lived work, to recover the details of curriculum design and development as practical action, to show how, in particular practice domains, learning in the here-and-now provides the grounds for learning as preparation and to recover the details of ‘ambient practice’ as a basis for curriculum design and development