Preface T he 21st century will be described as the century of infectious diseases. This is not only because of the increasing number of new infections, such as severe acute respiratory syndrome, the H1N1 pandemic or the spread of West Nile virus and dengue fever, but also because the role of infection in the pathogenesis of chronic diseases has been recognised and is now better understood. Chronic bronchial infection plays a role in the progression and prognosis of many lung diseases but also contributes to a systemic inflammatory response, which is a predisposition for extrapulmonary diseases such as arteriosclerosis or diabetes mellitus. At present, the mechanisms that contribute to chronic pathogenic colonisation of the lower respiratory tract are not entirely clear. Is there a defect of the innate or the adaptive immune system of the lung favouring chronic colonisation? Are there deficits in the innate and/or adaptive immune system on a local pulmonary level that contribute to the primary colonisation and secondary tissue damage? What is the role of air pollution and other environmental factors? Many questions about chronic bronchial infection are unclear. Is it possible to prevent this condition by early, adequate treatment of the underlying disease or is it better to stimulate an immune response by vaccination or similar immunomodulatory agents? Is it possible to influence the course of the disease by treating chronic pulmonary infection? How long should the treatment period last for? Should the patient receive the same treatment strategy or should different treatment be administered at different time-points? This issue of the European Respiratory Monograph (ERM) summarises the current understanding of chronic bronchopulmonary infections and addresses future needs. I would like to congratulate the Guest Editors, Francesco Blasi and Marc Miravitlles, for their tremendous work in bringing together this cutting-edge ERM, which should be of interest for general medical doctors and respiratory physicians, as well as infectious diseases specialists. In addition, it will provide guidance for future basic and clinical research. I am sure that readers from different areas of respiratory medicine will find this ERM useful in their daily practice. Eur Respir Monogr 2013 60: v. Copyright ERS. DOI: 10.1183/1025448x.10005813. Print ISBN: 978-1-84984-034-7. Online ISBN: 978-1-84984-035-4. Print ISSN: 1025-448x. Online ISSN: 2075-6674. v