Treat-all involves regular HIV testing and prompt initiation of ART for all those diagnosed HIV-positive, regardless of immunological status, aiming to improve health outcomes and reduce HIV incidence. It is a biomedical and social approach to HIV treatment and prevention, requiring active engagement of individuals. Questions remain as to how Treat-all will be experienced, interpreted and understood by people living with HIV, how ART initiation will be decided upon in the absence of clinical symptoms of disease, and how ongoing engagement with care will be navigated over time. This thesis aims to investigate how clinically asymptomatic people living with HIV experience engagement with HIV treatment and care under Treat-all, situated within a Médecins Sans Frontières/Eswatini Ministry of Health Treat-all pilot in Shiselweni, southern Eswatini. Research comprised 145 interviews, conducted February 2015 – September 2017, including repeated interviews with 30 people living with HIV, one-time interviews with 28 people living with HIV, and one-time interviews with 31 health care workers. Additionally, observations and focus group discussions were conducted. Data were analysed thematically, drawing upon principles of grounded theory to generate findings inductively from participant accounts. Nvivo 11 aided analysis. This research highlights the individually varied, potentially complex processes of coming to terms with an HIV diagnosis and deciding when to initiate ART, and the dissonance between biomedical interpretations of treatment necessity and individuals’ decision-making processes and treatment readiness. It appears important for individuals to perceive need for treatment, have choice regarding when to initiate ART, to feel ownership over the management of their health and treatment-taking, and to have evidence of the treatment’s effectiveness to motivate treatment-taking and engagement with care. Doubts about diagnosis accuracy, treatment need and effect could undermine engagement and cause intermittent treatment-taking. Stigma persists in the context of Treat-all, driving engagement with treatment to avoid symptom development and status exposure, and also undermining engagement and causing treatment-taking fragility. As settings implement Treat-all, it is imperative to understand, reflect upon and address the views and experiences of people living with HIV, and to ensure programmes meet individuals’ needs. This thesis aims to contribute towards this understanding.