We appreciate all the kind remarks and suggestions from the many medical students over the past 3 years. Your positive reception has been an incredible encouragement, especially in light of the short life of the Case Files® series. In this fourth edition of Case Files®: Pediatrics, the basic format of the book has been retained. Improvements were made in updating many of the sections. New cases include sickle cell disease, rectal bleeding, juvenile idiopathic arthritis, primary syphilis, pityriasis rosacea, and congenital cataracts. We reviewed the clinical scenarios with the intent of improving them; however, their “real-life” presentations patterned after actual clinical experience were accurate and instructive. The multiple-choice questions have been carefully reviewed and rewritten to ensure that they comply with the National Board and USMLE format. Through this fourth edition, we hope that the reader will continue to enjoy learning how to diagnose and manage patients through the simulated clinical cases. It certainly is a privilege to be teachers for so many students, and it is with humility that we present this edition.