In this chapter, the main examples of Hippocratic expository prose–written for oral delivery–focused on in this study are introduced in the context of the Hippocratic Collection and of the complex shifts influencing the development of prose in the late-fifth-century intellectual Greek world; namely, the ongoing transition from poetry as the dominant form of authoritative communication to prose and the development of an ever-greater reliance on the written word and concurrent changes to the status of oral communication.