Preface There is no question about it: in terms of morbidity and healthcare costs, asthma is the most important respiratory disease in children and adolescents. Both research and clinical development have been tremendously successful over the last few decades, and understanding about the genetics, molecular biology, pathophysiology and clinical implications of asthma have been greatly improved. We have become aware that paediatric asthma is not a homogenous disease, but is very heterogeneous, with various clinical phenotypes that need different diagnostic and therapeutic approaches. Like bronchial malignancy, asthma may be one of the first diseases in which personalised, phenotype-driven medicine could be possible in the next few years. However, such an approach will not only have medical implications but will raise a number of questions with regard to educational programmes for physicians and patients, and will give a focus on pharmacoeconomic considerations. Asthma research driven by paediatricians has produced impressive results in the past, and this will also be the case in the future. The winners of all of these ongoing efforts are the patients, as good research leads to better care with an improved quality of life. This issue of the European Respiratory Monograph summarises the current knowledge on paediatric asthma but also focuses on future developments. I want to congratulate the Guest Editors for this excellent Monograph, which should be of interest to paediatricians but also to general medical doctors and pulmonary specialists treating adults. I am convinced that they will find this Monograph useful in daily practice. Editor in Chief Tobias Welte Eur Respir Monogr 2012 56: vi. Copyright ERS 2012. DOI: 10.1183/1025448x.10018610. Print ISBN: 978-1-84984-019-4. Online ISBN: 978-1-84984-020-0. Print ISSN: 1025-448x. Online ISSN: 2075-6674. vi