This book is a concise textbook of Pediatrics that focuses on what the medical student needs to know during the core pediatric clerkship. It achieves this by addressing the essential aspects of pediatric health and illness within the special educational needs of the medical student and starting house officer. Nelson Essentials of Pediatrics has become established as one of the leading core textbooks for medical students, house officers, and residents in non-paediatric specialties. It is also widely used by nurse practitioners. The 4th edition will continue to be strong in its appeal to these groups. This is not an abridgment or condensation of the Nelson Texbook of Pediatrics which is our primary clinical reference work in Pediatrics. Rather, the book was developed and written fresh with the medical student audience in mind.