In France, since 2000, undocumented immigrants’ healthcare expenses have been covered by a welfare benefit called “State Medical Aid” (Aide médicale de l’État, AME), distinct from the state health insurance scheme (assurance maladie). Based on research tracing the genesis of AME and carried out in a hospital, this article analyzes the consequences of the introduction of immigration administrative categories into the healthcare system, as well as the emergence of a downgraded form of social citizenship for people living illegally in France.