On parle dans sa propre langue, on ecrit dans une langue etrangere ["We speak in our mother tongue, but write in a foreign language"], says Sartre in Les Mots. But which "language" did Sartre use in his novels to render speech in writing? Understood as a true novelistic component of freedom, Sartre's deployment of dialogue meets three major guidelines. First, in order to avoid imposing an omnipotent narrator on the reader, Sartre refuses to shorten his character's conversations; therefore the reader confronts the scrupulous use of direct speech, which differentiates Sartrean dialogues from those staged by his contemporaries. Influenced by Dostoyevsky, he also seeks to resort to the hesitation and superfluousness of speech's trials and errors, rather than to the speed and clarity of dramatic language which would entail the characters' unrealistic self-consciousness. Finally, Sartre admits that dialogue can be "heavy" and may not contribute to the action of the novel without a cost. The purpose of my article is to present such a Sartrean poetics of dialogue and then to examine, by looking at the whole corpus of his novels, its implications for narratology and stylistics.