This book presents an analysis of professionalism as defined and enacted by subject teaching associations. These organisations operate throughout the world as professional teacher communities and representative organisations. The analysis presented herein is part of a large doctoral project which employed critical qualitative inquiry to compare the contribution that two subject teaching associations (history and science) make to the project of teacher professionalism. The book details how the initial project focus was on examining professionalism as an active process of engagement through which teachers, as members of subject associations, seek greater influence in determining the policies and practices that govern their worklives. However, because the study was undertaken during a period of sweeping syllabus change in Australia, attention also focused on how associations respond to a rapidly changing policy context. The efforts of associations to assert a participative and teacher-centred form of professionalism, within a context of competitive and sometimes conflictual relations with education bureaucracies are illuminated herein.