Advances in health, access to care, and prevention do not benefit everyone. While life expectancy continues to rise, inequalities persist and are even widening. This special report has two objectives: 1) to provide readers with the fundamental knowledge needed to understand what health inequalities are and how they arise; 2) to identify intervention strategies—based on scientific analysis in which the social sciences play a major role—to combat these inequalities; and to analyze the actions and programs designed to achieve this goal.