More than ever are we facing the challenge of providing evidence that what we do responds to priority health needs and challenges of the ones we intend to serve: patients, citizens, families, communities and the nation at large. Which are those health needs and challenges? Who defines them? How do medical schools organize themselves to address them through their education, research and service delivery functions? Principles of social accountability call for an explicit three-tier engagement: identification of current and prospective social needs and challenges, adaptation of school's programmes to meet them and verification that anticipated effects have benefited society. Measurement tools need to be designed and tested to steer development in this direction, particularly to establish a meaningful relationship between inputs, processes, outputs and impact on health. The Global Consensus on Social Accountability of Medical Schools provides a unique opportunity to foster collaborative research and development in an area of great significance for the future of medical education.