From November 1954 to November 1956, Canadian nurse Margaret Campbell Jackson was employed by the World Health Organization (WHO) and was stationed in Tehran, Iran, where she participated in the establishment of a Maternal and Child Health (MCH) Centre. The objective of the project, known as Iran 10, was twofold: to set up a health service for mothers and children and to initiate a field training program for Iranian physicians, nurses, and other health care providers. Drawing on 180 letters Jackson wrote to her family in Canada from Iran, this article analyzes the MCH Centre as a contact zone and considers the relationships Jackson developed with staff affiliated with the project. The Centre became a space of cross-cultural encounters, where locally and foreign-trained Iranian staff and expatriates mingled and shared working relationships. I argue that authority was negotiated and contested through interactions and associations that were often unequal and framed by notions of progress, modernization, race, and health. Personality also played an important role.