I entered the gene therapy field in the mid-1990s, being fascinated by the immense potential of genes as drugs for the treatment of human disease. Since then, I have experienced the ups and downs of this discipline, and tried to contribute with my work and that of my laboratory to the development of innovative approaches to the treatment of cardiovascular disorders. During these years, I have had several opp- tunities to speak on gene therapy at lectures and academic lessons, and have often noticed that the field is very attractive to scientists of all disciplines. However, as yet no comprehensive book on the subject has been published. Indeed, most books in the field are either a collection of gene transfer laboratory protocols or deal with the subject in a rather superficial manner. Hence the idea to write a gene therapy textbook that is broad and comprehensive, but at the same time provides sufficient molecular and clinical detail to be of interest to students, professors, and specialists in the various disciplines that contribute to gene therapy. I have tried to keep the language plain and, whenever possible, non-technical. Since the book is intended to be a textbook in the field of gene therapy in both the basic science and clinical areas, whenever technical descriptions are required, they are provided.