Much of the current social science literature on the clinical trials industry focuses on the profit-seeking practices adopted by pharmaceutical companies and the contract research organisations they employ to enable the mass production and distribution of their products. However, what the current literature demands is further ethnographic engagement with the particularities of the diseases being investigated, the local contexts and histories in which they are entwined, and how these impact the affective relationships between clinical research organisations and their participants. On the basis of ethnographic research with a nonprofit clinical research organisation specialising in TB vaccinations in South Africa, I argue that the complexities of TB mean that research into it necessitates frequent and often intimate interactions with research participants. These were perceived by researchers to yield opportunities to take an interest in the physical and psychosocial wellbeing of research participants which went beyond and sometimes ran into conflict with the requirements of protocol. The aim of this paper is to advocate more finely tuned attention to the challenges posed by the clinical trials industry today, an attention sensitive to the particularities of the contexts of clinical trials.