The core of the work described in this paper is a small-scale qualitative research project based on the classroom observation of student teachers in England following a 1-year "PGCE" (postgraduate continuing education) course in 1992. This project was underpinned by an exploration of a theoretical model of the nature of the relationship between practice and theory and formed an initial attempt to develop a practical dialogic methodology for co-operative reflection on professional practice: in this case for both student teachers and their trainers. The classrooms under consideration were mathematics and modern language classrooms in British secondary schools. Part 1 of the paper raises issues about co-operative action and its place within educational research. Part 2 offers a brief discussion of the nature of the relationship between theory and practice together with an attempt to construct a three-level triadic model to show how this applies to professional training. This model is used later in the paper as a framework for discussion of students' practice and the theories and range of practices of teacher educators. Part 3 focuses directly on four student teachers' behaviors and their theories. Part 4 explores the processes used by the trainers to articulate their theories about their professional work. Part 5 looks directly at some of the hypotheses and questions about classrooms and about knowledge of the professional practice of teacher educators raised through the work of the project. Part 6 offers a summary of the ad hoc dialogic methodology employed during this work. (Contains 24 references and provides a list of the 27 occasional papers published by the Centre for Language in Education.) (Author/ND)