In Medieval French, the syntax of the subject was far freer than it is today. It was mainly conditionned by pragmatic factors, and was therefore more meaningful. This paper focuses on the personal pronoun "he", and tries to account for the different values associated with its different positions. We show the presence of complementary distribution phenomenons, in particular between the utterances with "he + verb" and those with "verb + he" . This is particularly the case with regard to the intial elements, which have an influence on the interpretation of the whole utterance. More precisely, it appears that the utterances with a postverbal subject are characterised by different sorts of disruptions with respect to the preceding context. We moreover question the status of the evolution of the syntax of the subject personal pronoun as a real case of grammaticalization.