In this article I elaborate a theoretical framework for examining teacher professionalism as an enacted discourse of power. Central to this framework is an understanding of professionalism as a process that relates to the ways teachers attempt to influence the quality and character of their work. For subject teaching associations this process connects to issues of power such as teacher participation in educational policy-making, and the advocacy of subject interests. In this article I theorise professionalism as enacted by subject teaching associations, arguing that the enacted form is shaped by changing structural, cultural and agential variables. Finally, I explore the interactive relationship between structure, culture and agency in the work of subject teaching associations, and present a working model through which enacted professionalism may be analysed and interpreted. (Contains 1 figure and 7 notes.)