For all their concern with the nature of medical authority, historians of medicine have paid remarkably little attention to the history of the medical script, the main medium in and through which the doctor’s authority is enacted. This essay analyzes the medical prescription as an instance of a written performative. While focusing on the changing uses of one particular documentary genre in turn-of-the-twentieth-century France, it seeks to outline a broader theory of graphic performativity, or of the conditions under which the symbolic power of the oral performance is transferred and transformed as it is transcribed on paper.