The objective of this paper is to capture the extent of sectoral heterogeneity across Professional Service sectors. It is argued that ongoing scholarly disputes on their boundaries within the geography of industry have lost sight of the intrinsic diversity that characterizes these activities. The present study connects this cue to research on sectoral patterns and elaborates an empirical analysis of employment structures and the associated skill bases of professional service sectors. Through this focus we are able to frame the emergence of cross-sectoral variety in the context of evolving specialization.