HIV testing services (HTS) are an essential component of a national response to the HIV epidemic, and in lower and middle income countries, at least 150 million persons are tested annually. HIV testing is necessary to identify persons in need of antiretroviral treatment, which has been documented to be highly effective not only for treatment but also for prevention of HIV transmission to both adults and children. An assessment of the recent literature on sustainability of health and HIV services suggests that organizational performance, flexibility, and integration with other health interventions contribute to sustainability of HIV services and programs. This article describes the experiences of two HIV testing service providers in Uganda and Zambia as well as the track record of services to prevent mother-to-child HIV transmission to illustrate the factors of performance, flexibility, adaptability, and integration which are key to the sustainability of HIV testing services.