This book offers a genealogy of the medicalisation of sexual appetite in Europe and the United States from the nineteenth to twenty-first century. Histories of sexuality have predominantly focused on the emergence of sexual identities and categories of desire. They have marginalised questions of excess and lack, the appearance of a libido that dwindles or intensifies, which became a pathological object in Europe by the nineteenth century. Through a genealogical approach that draws on the writings of Michel Foucault, examines key ‘moments’ in the pathologisation of sexuality and demonstrates how medical techniques assumed critical roles in shaping modern understandings of the problem of appetite. It examines how techniques of the patient case history, elixirs and devices, measurement, diagnostic manuals and pharmaceuticals were central to the medicalisation of sexual appetite. Jacinthe Flore argues that these techniques are significant for understanding how a concern with ‘how much?’ has transformed medical knowledge of sexuality since the nineteenth century. The questions of ‘how much?’, ‘how often?’ and ‘how intense?’ thus require a genealogical investigation that pays attention to the emergence of medical techniques, the transformation of forms of knowledge and their effects on the problematisations of sexual appetite.