Global expansion of antiretroviral therapy (ART) programmes for people living with HIV is the largest public health undertaking to date. Antiretroviral therapy adherence drives individual and programme outcomes, yet little is known regarding the determinants of these behaviours. We investigated beliefs and practices associated with ART use in Cambodia. In-depth interviews were conducted during 2005 with 27 people living with HIV who were recruited using a theoretical sampling strategy and analysed in Khmer and English using an inductive approach to code data and identify themes. Limited access to ART generated a sense of ART as rare and precious, with access granted by doctors once patients proved themselves dependable. The social construction of ART use was strict, precise and modern with ritualistic preparation and dosing procedures. Experiences of life-saving efficacy in self and others built a deep sense of trust. For many, ART was simply equated to life. Antiretroviral therapy dosing was prioritized and supported by an ever-present sense of remembering, reminder devices and social networks. Healthcare workers set norms and provided various forms of adherence support. Antiretroviral therapy use in Cambodia is shaped by the relationship between individuals and social and healthcare networks that set, encourage and enforce precise norms of ART use.