Inequalities in the health sector are a phenomenon that occurs in all countries of the world, even in the most developed ones. Despite the fact that the level of health of the population worldwide has shown a remarkable improvement in recent decades, social inequalities in health have not only not decreased, but in several cases have widened. The purpose of this book is the theoretical approach to the phenomenon of health inequalities today. A key research issue is the identification and analysis of the causes and factors that contribute to the creation of social inequalities, both at the level of the population's health and in access to health services.