The 19 chapters that have been extensively revised, with new authors added in several cases, reflect the substantially updated material in each of their areas of pediatric medicine. Especially important are updates to the chapters on immunizations, endo-crinology, neurologic and muscular disorders, and adolescence. The chapter on HIV includes current guidelines for prevention and treatment of HIV and updates information on the new antiretroviral therapies that have become available. The chapter on immunizations contains the most recently published recommendations, discusses the contraindications and precautions relevant to special populations, and includes the new vaccines licensed since the last edition of this book. Chapters on adolescence, skin, immunodeficiency, inborn errors of metabolism, and neoplastic disease are markedly updated with the latest information. All laboratory tables in Chapter 46 Pediatric Laboratory Medicine and Reference Ranges that includes reference ranges and reference intervals have been updated. All other chapters are substantially revised and references have been updated. Twenty-six new authors have contributed to these revisions.