The Rare Diseases Epidemiology book is a comprehensive text focused on the rare disease field where both general epidemiological methods and specific methods for low prevalence diseases are discussed. This is the first book to address rare diseases as a public health problem where the epidemiological research constrains are analyzed and at the same time, solutions and also data by rare diseases groups are provided. This book is probably a starting point for developing better future epidemiological research programs on rare diseases, and also research strategies in fields such as health planning and decision making, which will be able to promote not only new knowledge but also capacity building for policy makers. Epidemiology is always mentioned in all rare diseases policy documents as an important topic but a comprehensive book on this discipline applied to rare diseases, had never been written before.