This book has become the standard reference text on respiratory diseases in children. It has been extensively revised and updated to encompass the latest developments, and there are now specific chapters on obstructive sleep apnoea and the lung in HIV infection. The biggest revisions to existing chapters are in those on growth and development, respiratory noises, cough and pulmonary consequences of inhalation. The clinical approach in this book is strongly based on an understanding of epidemiology, pathophysiology and increasingly, molecular biology. This fourth edtition brings a stronger theoretical basis to the clinical practice that has been one of the strengths of previous edtitions.