Abstract: Between 1923 and 1925, tropical medicine specialist, Cecil Cook, conducted a field survey of leprosy in Australia. The disease, once largely confined to the east, had infiltrated the north of the continent. Mostly, Indigenous people were afflicted but endemicity was present among white Australians in regions of interracial contact. Cook criticised state government control measures and recommended the standardisation of policy under federal government authority. Drawing from international precedents and biomedicine, adapted to local epidemiology, Cook and his colleagues in Australian health bureaucracies determined leprosy policies in the interwar period. As white settlement of the north expanded, a major aim was to protect white Australians from the presumed threat posed by Indigenous people with infectious diseases. Concomitantly, concern for the health and welfare of remote Indigenous Australians found expression among humanitarians, Indigenous activists, missionaries, and anthropologists, with their agitation for change and giving relief and protection at missions, sometimes subverting leprosy laws. Resultant inquiries did little to lessen harsh leprosy policy. Between 1931 and 1940, leprosaria for Indigenous patients opened in the Northern Territory, north-west Western Australia, and northern Queensland—Channel Island, Derby, and Fantome Island, respectively—supported by funded field surveys and stronger legal powers for examination and detention.