This report presents the findings of a large spatial analysis of almost 3 million viral load tests from over 2 million HIV patients on antiretroviral therapy in South Africa. It is part of the second phase of a series of analytical and evaluation studies contributing to the design of an impact and process evaluation of South Africa’s National Adherence Guidelines for Chronic Diseases. The analysis was conducted by the National Health Laboratory Service (NHLS) and Boston University/Health Economics and Epidemiology Research Office (HE2RO), in collaboration with the National Institute for Communicable Diseases (NICD), the National Department of Health of South Africa, and the World Bank. A number of other institutions contributed in the multi-step process of creating a patient-linked cohort through a novel record linkage algorithm and a masterlist of public sector health facilities, which are both underpinning this analysis and described in the report. The analysis demonstrates the diversity in the proportion of HIV patients getting a viral load test annually and patients virally suppressed. The variation shows by geographic location and facility, as well as by age, gender and demography. It sheds light on high viral load levels in young HIV patients on treatment. Also, one in six male and one in nine female ART patients were identified as having a high risk of HIV transmission due to viral load levels above 10,000 copies/mL