In this paper I present a model of professional knowledge forms that accounts for the different, and sometimes contradictory, ways in which medical doctors (MDs) and various complementary and alternative medicine (CAM) practitioners define their competencies and make legitimacy claims. The first section provides a schema for problematising knowledge and its relationship to legitimacy by distinguishing between the context, form and content of professional knowledge. I draw particularly upon Jamous and Peloille's (1970) distinction between the technical or indeterminate forms of professional knowledge. I argue that their characterisation might be enriched by attending to dimensions of 'exclusive' versus 'everyday' knowledge forms. In particular, I point out that both technical and indeterminate forms are amenable to exclusion, or conversely can be made accessible as everyday knowledge. Both forms can thus be employed in attempts to legitimate professional practice. In the final section, I map the current context of CAM and biomedicine onto this expanded professional knowledge map.