South Africa continues to bear a heavy burden of HIV and a significant proportion of the nation's population consists of immigrants from other severely afflicted African nations. Yet little is known about how migrant populations respond to HIV in shifting cultural and clinical landscapes. Analysing 21 ethnographic life history interviews, this paper explores the social complexities of living with antiretroviral therapy and disclosure of serostatus among HIV-positive Mozambican migrants in Johannesburg. It focuses on (i) conceptualising the 'biosocial ambiance of illness'; (ii) how transformations occur in perceptions of disease; and (iii) how stigma produces an ambit of loneliness and secrecy, which inflects disclosure unevenly in different life-spaces and health-worlds. The net effect of these three processes is a silence which is detrimental to the social normalisation of HIV, treatment-seeking and clinical drug adherence, which in turn may increase rates of morbidity and mortality and contribute to drug resistance.