Preface John R. Hurst It is a pleasure to introduce and recommend to you this latest edition of the ERS Monograph, which covers the important and neglected topic of complex breathlessness, here defined as breathlessness where the cause remains unclear or appears disproportionate to any underlying conditions. Complex breathlessness is challenging both to people living with this problem, and to clinicians leading assessment and management. And that’s where this collection really excels – providing a clear, concise and yet authoritative, comprehensive and systematic approach to investigation and treatment. It’s a must-read, and so I congratulate the Guest Editors James H. Hull and Jemma Haines on delivering this excellent collection, which deserves a place on the (e-)shelf of every practising respiratory clinician. To end on a personal note, this is the last Preface I will write as Editor in Chief, as I hand over the Monograph to the experienced hands of Professor Peter M.A. Calverley. Thank you to everyone who has contributed as an Editorial Board member, Guest Editor, author and reviewer over the past few years, giving freely of your time and expertise to the benefit of our Society. Special thanks to the ERS Publications Office team, Caroline Ashford-Bentley and Rachel Gozzard without whom, quite literally, there would be no Monograph! Peter, over to you. Disclosures: J.R. Hurst reports receiving grants, personal fees and non-financial support from pharmaceutical companies that make medicines to treat respiratory disease. This includes reimbursement for educational activities and advisory work, and support to attend meetings. Copyright ©ERS 2022. Print ISBN: 978-1-84984-151-1. Online ISBN: 978-1-84984-152-8. Print ISSN: 2312-508X. Online ISSN: 2312-5098. https://doi.org/10.1183/2312508X.10015622 vii