Infection by Helicobacter pylori has for many years been one of the medical conditions most studied not only in the gastroenterological context. This is because, in recent years, H. pylori has also been involved in a number of extra-intestinal diseases. In this book, we have tried to involve the biggest international experts on the subject. Some authors have tried to provide a complete view of the most common and widely used diagnostic methods, both invasive and non-invasive, also explaining the unusual techniques and the most innovative complementary methods not yet used in clinical practice. Other international experts have tried to describe the latest findings on pathogenesis and the various clinical manifestations of infection by H. pylori in the various systems. One chapter is reserved for H. pylori infection in childhood, an important period especially in transmission of the infection, explaining the various international guidelines for correct diagnosis and treatment. The authors have also provided the latest evidence regarding the various methods of eradication therapy, with a critical analysis of the reasons that compel some researchers to believe that eradication at all costs is not always correct and useful for humans. The book also deals with the current and latest knowledge regarding the progress and the difficulties in the development of a vaccine against H. pylori infection, the implementation of which could solve the problem of the difficulty in the eradication linked mainly to the onset of antibiotic-resistance.