Navigating this ever-changing field is the major purpose of this ERS Monograph, through summarised information on all major pleural diseases, written by experts in the field who have often contributed directly to the evidence base. The Monograph therefore covers aspects of background and investigation, including epidemiology [1], physiology and its relationship to symptoms and management [2], basic science and animal models of pleural disease [3], the role of radiology [4] and ultrasound [5], which is now considered an essential tool for pleural disease management. We have also included chapters on the major pleural entities including pleural infection [6], MPE [7], mesothelioma [8], pneumothorax [9], TB [10] and non-specific pleuritis [11]. Finally, liaison with other specialities and delivery of a pleural service has been addressed through chapters on surgery for pleural disease [12] and the key components of an active pleural service [13]. We hope that this Monograph will serve as an up-to-date resource for clinicians wishing to understand how to investigate and manage an array of pleural disease on the basis of evidence, thereby improving delivery of care, and expanding awareness of the development, biology and progression of pleural conditions. As a highly active research field, we also hope that this Monograph will inspire further studies and research programmes, and we have asked our authors to highlight areas in which evidence is lacking to promote this important goal. It has been a privilege to edit this Monograph the many contributing authors are leaders in their respective fields, and we feel this has created a highly focussed and relevant piece of work that will improve practice. We would like to thank the contributors for their input in the context of busy clinical and academic practices, and the European Respiratory Society for taking forward this much needed work. References 1. Bodtger U, Hallifax RJ. Epidemiology: why is pleural disease becoming more common? In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 1–12. 2. Thomas R, Lee YCG, Mishra EK. The pathophysiology of breathlessness and other symptoms associated with pleural effusions. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 13–28. 3. Yao X, Kanellakis NI. In vitro and in vivo laboratory models. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 29–47. 4. Duerden L, Benamore R, Edey A. Radiology: what is the role of chest radiographs, CT and PET in modern management? In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 48–72. 5. Banka RA, Skaarup SH, Mercer RM, et al. Thoracic ultrasound: a key tool beyond procedure guidance. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 73–89. 6. Bedawi EO, Rahman NM. Pleural infection: moving from treatment to prevention. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 155–171. 7. Arnold DT, Roberts M, Wahidi M, et al. Optimal diagnosis and treatment of malignant disease: challenging the guidelines. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 138–154. 8. Bibby AC, Blyth KG, Sterman DH, et al. Mesothelioma: is chemotherapy alone a thing of the past? In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 232–249. 9. Hallifax RJ, Walker S, Marciniak SJ. Pneumothorax: how to predict, prevent and cure. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 193–210. 10. Shaw JA, Ahmed L, Koegelenberg CFN. Effusions related to TB. In: Maskell NA, Laursen CB, Lee YCG, et al. Pleural Disease (ERS Monograph). Sheffield, European Respiratory Society, 2020 pp. 172–192. https://doi.org/10.1183/2312508X.10004320 ix