As recommended by the UNAIDS Programme Coordinating Board (PCB) in 1997, the UNAIDS Monitoring and Evaluation Reference Group (MERG) was established in 1998 to advise UNAIDS on monitoring and evaluation (M&E) at all levels of the Programme. The MERG – which replaced the PCB Working Group on Indicators and Evaluation – meets annually, bringing together the UNAIDS Secretariat and Cosponsors, donors, NGOs and technical experts in the field of M&E. Since 1998, the MERG has contributed substantively to the strengthening of M&E within UNAIDS and has played a critical role in harmonizing and setting the international standards for national indicators, global M&E guidelines, training curricula, and tools for use at country level by national AIDS programmes and by UN partners.

Since 2001, a significant focus of the MERG has been on establishing and refining the global indicators for monitoring the global response and tracking progress of all countries towards meeting the UN General Assembly Special Session on AIDS (UNGASS) Declaration of Commitment. To achieve these, the most recent focus of the MERG has been on strengthening the coordination, M&E plans, data quality, and capacity at global, regional, and national levels to support a unified national M&E system, known as the ‘Third One” of the “Three Ones” principle – one National Coordinating Authority, one agreed National Action Plan, and one national M&E system