This book presents the research results obtained by Grupo de Equidad en Salud (Health Equity Group), in relation to the development of an indicator of inequity in avoidable mortality, consisting of a methodology that allows knowing, in a consolidated way, the state of the inequality in avoidable mortality based on the variants included in the development of the indicator itself; also, an analysis of global and local data allows realistically understanding the dimension of the problem in both contexts. This book provides additional elements of analysis in order to assess the inadequate role of health systems in solving the most sensitive problems affecting vulnerable populations. On the other hand, conceptual elements around the issue of inequity, as well as the results of a systematic review of the literature related to the different ways of measuring disparities, gaps or inequities in health, are presented here to help the reader approach the development of new conceptual or measurement proposals. This book is intended to contribute to the understanding of the issue, and to encourage joint solutions to avoidable problems of high social cost.