ERS | monograph Preface Tobias Welte (outgoing Editor in Chief) and Robert Bals (incoming Editor in Chief) After arteriosclerosis and stroke, COPD is one of the most common diseases worldwide. The morbidity, mortality and healthcare costs of COPD are high and will continue to rise due to the demographic changes expected. Since the beginning of the millennium, COPD has become one of the major areas of research. The improvement in quality of life, and perhaps in life expectancy, achieved since then is primarily due to the establishment of non-pharmacological measures, such as standardised smoking-cessation programmes, structured exercise therapy, and infection prevention with influenza and pneumococcal vaccination. Progress in pharmacological therapy, however, has been low. The essential treatment components, such as β-mimetics, anticholinergics or ICSs, have been available for more than 50 years, and have improved in terms of duration of action, efficacy and mode of administration. However, more than 15 substances with new and different modes of action tested in clinical trials have failed to demonstrate activity and have not been approved for regular treatment. The dynamic development of new therapies for asthma may explain why most of the COPD substances failed. Better phenotyping of asthma patients made targeted pathophysiology-oriented treatment possible. COPD is a heterogeneous disease, and it is indisputable that there are different phenotypes however, with the exception of α1-ATD, these have not been well characterised in the past. Better characterisation of COPD patients using new biomarkers, advanced imaging properties and the whole spectrum of omics technology may stimulate the development of a new generation of drugs. This issue of the ERS Monograph provides a comprehensive overview of the debate in this context, with consideration of the future direction of COPD research and clinical practice. We would like to thank the Guest Editors Antonio Anzueto, Yvonne Heijdra and John R. Hurst for their excellent work in bringing together this interesting and wide-ranging selection of chapters. We hope that both clinicians and scientists will find this book Copyright ©ERS 2015. Print ISBN: 978-1-84984-063-7. Online ISBN: 978-1-84984-064-4. Print ISSN: 2312-508X. Online ISSN: 2312-5098. Tobias Welte Robert Bals ERS Monogr 2015 69: vii–viii. DOI: 10.1183/2312508X.10008315 vii