This article addresses how French academics, doctors and state bureaucrats formulated sex work as a pathology, an area of inquiry that had to be studied in the interest of public safety. French colonisation in the Levant extended the reach of this ‘expertise’ from the metropole to Lebanon under the guise of public health. Knowledge produced by academics was used to buttress colonial state policy, which demanded that sex workers be contained to protect society against medical contagion. No longer drawing conclusions based on speculation, the medical establishment asserted its authority by harnessing modern advances in science and uniting them with extensive observation. ‘Empirical facts’ replaced ‘opinions’, as doctors forged new approaches to studying and containing venereal disease. They accomplished this through the use of statistics and new methods of diagnosing and treating maladies. Their novel approach was used to treat sex workers and to support commercial sex work policy both at home and abroad. Sex workers became the objects of scientific study and were consequently problematised by the state in medicalised terms.