Museum professionalism remains an unexplored area in museum studies, particularly with regard to what is arguably the core generic question of a "sui generis" professional knowledge base, and its necessary and sufficient conditions. The need to examine this question becomes all the more important with the increasing expansion of the museum's roles and functions. This paper starts by mapping out the policy and organizational context within which the roles of museums have expanded in the UK. It then situates the discussion of museum professional knowledge within a cross-disciplinary matrix bearing on the question of what is professional about occupations classified--or classifiable--as professions. Against the backdrop of the current organizational context of the museum as well as theories of professional knowledge, it highlights the ways in which museum work, more specifically museography, poses a distinctive set of questions compared to other "professional" fields; the paper thus homes in on the question of what it is that constitutes the uniqueness of museum professional knowledge in relation to museographic practice and the type of professional knowledge and expertise that can sustain it and enact its creative and educational potentials and affordances.