This Global Health Workforce Alliance report argues that critical shortages in the health workforce in many developing countries pose a significant challenge to the achievement of universal health coverage and the Sustainable Development Goals. Increasing attention has therefore been focused on the potential of community health workers (CHWs) to expand access to essential health services, particularly in low- and middle-income countries. The term CHW is broad, and CHWs can be defined as health workers who have been trained to some extent but do not possess a formal professional certificate, many live and work in the community. It encompasses a wide range of health workers, paid and unpaid, professional and lay, experienced and inexperienced, including traditional birth attendants, village health workers, peer supporters, community volunteers and health extension workers. The study found ‘promising evidence that they can be cost-effective in certain contexts and under certain circumstances’.