This article analyzes in detail the emergence of topic markers in Clasical French : en/pour ce qui concerne, en/pour ce qui regarde, et en/pour ce qui touche (lit. « in/for what concerns, looks, touches », all meaning « concerning »). These constructions followed the usual evolutionary path, from linked adverbial to thematic function, then to topic function. The author examines in detail the contexts in which these constructions undergo reanalysis, and focuses on two criteria, morpho-syntax and topic/comment. It can be shown that the opposition between en and pour is meaningful : pour is found indifferently for all uses, while those containing en are usually restricted to intrapredicative postverbal uses.