According to the Joint United Nations Programme on HIV/AIDS (UNAIDS), in 2018, an estimated 37.9 million people were living with HIV worldwide. There were also 1.7 million new infections and 770,000 deaths. At the end of June 2019, 24.5 million people were receiving antiretroviral therapy (ART). Nonetheless, increased access to high-quality ART services is needed to further reduce mortality and new infections and to optimize long term outcomes. In this article, we summarize priorities for HIV service delivery research and guidance identified through a World Health Organization (WHO) consultation held at the end of 2018. The priorities identified include linkage from HIV testing to care; rapid initiation of ART (including out-of-facility ART initiation); task sharing and decentralization, including children and patients on second line; ART delivery for stable clients; adherence, retention, and reengagement in care; management of advanced HIV disease; provision of welcoming health services; and strengthening of service integration, particulary for NCDs and family planning. Ongoing evaluation is needed to determine the net effects of introducing differentiated service delivery models, in terms of health service inputs and long-term outcomes for people living with HIV.