Exchanges between medical and literary discourses in the French Renaissance: comparing the fascination with “des amas et pieces de chair informes” in Montaigne’s Essais and Joubert’s Erreurs populaires. Using Montaigne’s chapter “De l’oisiveté” as a point of departure, this article assesses the convergence of literary and medical discourses, and the significance of book-historical research. Since the “linguistic turn”, historians increasingly examine how medical texts crossed generic boundaries, sharing many strategies of literary discourse. Equally, recent attention, within book history, to “la politique éditoriale”, requires us to ask how early modern medical as well as literary books came into print and circulated. My comparison of Joubert’s Erreurs populaires (1578) and Montaigne’s Essais (1580), two surprising bestsellers, both published in Bordeaux by Simon Millanges, focuses specifically on the presentation of molar pregnancies by each author. I ask why this form of “monstrous birth” so fascinated the late Renaissance, and how far certain literary and medical styles of writing in the vernacular may have appealed to a common readership.