Taking action to reduce health inequalities is a matter of social justice. We need to confront the social gradient in health, not just the difference between the worst off and everybody else. Policies and interventions must not be confined to the health care system; they need to address the conditions in which people are born, grow, live, work, and age. Tackling the health gap will take action, based on sound evidence, across the whole of society. Sir Michael Marmot PhD ’75, MPH ’72, is an internationally acclaimed epidemiologist who has conducted seminal research into the social determinants of health for more than four decades. He will provide evidence that, as we look across countries, national policies make a difference and much can be done in cities, towns, and local areas to address the health gap.