Respiratory Syncytial Virus (RSV) is a ubiquitous and highly contagious virus belonging to the Paramyxoviridae family. RSV is the most common cause of bronchiolitis and hospitalisation during the first year of life and it might be associated with an increased risk of recurrent wheeze, asthma as well as with decreased respiratory function in school-aged children. In Chapter One, the authors report the most updated evidences for the environmental prophylaxis and summarise current recommendations about targeted palivizumab immunisation and ongoing trials on RSV vaccine development. Chapter Two summarises the most recent literature regarding acute bronchiolitis to provide an evidence-based approach to the management and treatment of this disease. In Chapter Three, the authors review risk factors associated with hospitalisation and pediatric intensive care unit admission. The final chapter illustrates a practical, pathophysiological and step up approach to children affected by severe bronchiolitis.