The social gradient in health has the clear implication that action to improve health and reduce inequalities has to take place at social level, not simply depending on individual changes. Individuals' ability to change is constrained by social circumstances. The evidence that the magnitude of the gradient varies between countries, and can change within a country over time, suggests that conscious strategies to change it can be successful. In my review of evidence in Britain, the Marmot Review, we made recommendations in six domains: give every child the best start in life; education and life-long learning; employment and working conditions; ensure that everyone has at least the minimum income necessary to lead a health life; healthy and sustainable places; taking a social determinants approach to prevention. A big question is the role of health professionals in action on social determinants of health. We have identified five actions in implementing recommendations: education and training; seeing the patient in broader perspective; the health service as employer; working in partnership; advocacy. The evidence is encouraging that health professionals can make a big difference in advancing the cause of health equity.