trengthening primary health care 1 and the attainment of universal health coverage 2,3 are both important current global health policy initiatives. Primary health care is essential and affordable care that is accessible to everyone in the community, and includes health promotion, disease prevention, health maintenance, education and rehabilitation. 4 The concept of universal health coverage, as noted in the United Nations' 2015 Sustainable Development Goals, is an aspiration to provide all people with access to essential high-quality health services and to safe, effective and affordable medicines and vaccines, while ensuring financial risk protection by providing care regardless of a person's ability to pay for it. 2,5 It is clear from these two definitions that there is overlap between the aims of primary health care and universal health coverage; indeed, many have noted that primary health care is essential to achieving universal coverage. 6,7 The two agendas have developed largely independently of each other, and yet the goal of both is to see healthier people living in healthier communities. There seems to be a natural synergy between the two. Yet the World Bank, the Bill and Melinda Gates Foundation and the World Health Organization (WHO) have referred to primary health care as a "black box" for policymakers 8-complex, mysterious and difficult to understand. Many health care policy-makers and funders have a poor understanding of primary health care, finding it difficult to quantify and assess its contributions to health systems. Here, we shine a light into the "black box." We emphasize the importance of performance indicators to monitor health system reform to show how strong primary health care contributes to the realization of universal health coverage.