This thesis examines how medical knowledge was circulated across Evangelical and imperial print networks between Britain and the South Pacific in the first half of the nineteenth century (ca. 1795-1850). It focuses on the London Missionary Society and draws upon a wide range of sources, including missionary letters, journals, administrative records, books, pamphlets and periodicals. It argues that missionary print production was not simply geared to the dispersal of fantastical imaginings into a British market. Rather, it was a complex, tangible, world-spanning system of knowledge production. This system encompassed the metropolitan accounts of the periodicals and the missionaries’ unpublished records, texts which documented moments of uncertainty, vulnerability and cross-cultural interaction on the edges of empire. Each chapter studies a particular medical theme in missionary writing: missionary medicine; disease and depopulation; the medicalisation of sexuality; childbirth; and death and dying. As the missionaries strived to investigate new ways of healing on the ground, their experiences of sickness and death played a significant role in shaping the knowledge networks that emerged between Britain and the South Pacific.