The purpose of this work is to rethink Michel Foucault's writings in the light of a notion - the notion of practice - whose strenght and interest will be emphasized. More specifically as an intensive and plastic notion and in contrast with a unifying concept. Indeed, at a time when practice emerges as a concept which has been philosophically, sociologically and politically overdetermined, Foucault follows his own path, both refusing to ascribe a synthetic function and a theoretical reach to practice. This approach particularly arose at the height of a central and decisive turning-point in his writings - in the early 70's - a practical moment this work aims at redifining and making stand out. Such a refusal of the theoretical synthesis is precisely linked with Foucault's original approach and with the specificity of the fields he explores. Since then, as regards this hypothesis, a new light is likely to be thrown on the genesis of his works. Given the first works are definitely characterized by a prominence of experience, a movement gradually comes into view making practice stand out from experience so as to reach the critical moment of the collapse of theory into practice, this one finally turning into the "practices of the self". Thanks to this process which points out the meaningful elements devoted to practice, it can then be seen that in the wake of the two major moments of Foucault's works - The Order of things ont he one hand, Discipline and punish, The Will to knowledge on the other hand - all the critical stakes are focused on the status given to practice which proves its importance in order to grasp Foucault's gesture.