The age old statement that “A properly taken history gives a diagnosis in 70% cases, physical examination adds another 20% and laboratory diagnosis is required in 10% cases” holds good also for the complicated cases admitted to the pediatric intensive care unit. A properly done clinical evaluation in such cases will help decide whether the child actually requires management in a pediatric intensive care unit or not. However, it should be emphasized that in certain situations, the seriously ill child may need clinical evaluation, laboratory investigation as well as initiation of treatment simultaneously. Moreover, any child admitted to a hospital ward may need ICU care with progress of the disease. Hence monitoring, clinical as well as laboratory as and when necessary, plays an important role to decide transfer of a child from the ward to a high dependency area or an ICU. A sharp clinical acumen therefore is a necessity. Organization of well-equipped PICUs with appointment of skilled nurses and trained doctors no doubt has a very important role in properly taking care of the seriously ill child. However, it needs mention that following well laid out treatment protocols uniformly by all the members of the team can go a long way in evidence based management as well as time to time modification and improvement of the protocols. The present book endeavors to put forward clinical and laboratory diagnostic aspects for some of the serious illnesses in children. Hope it will help the young doctors to make the habit of evidence based critical care in children. I am indebted to all my well wishers whose goodwill has encouraged me to write this book. I would like to offer my heartfelt thanks to Dr. Santanu Deb for meticulously going through all the chapters in the book with advice for addition and modifications and Dr. Rashna Das for going through few chapters with proper editing. Last but not the least, I am ever grateful to Mr. Pawaninder Vij, Director of Peepee Publishers and Distributors Pvt. Ltd., New Delhi for willingly accepting the task of publishing the book.