We appreciate all the kind remarks and suggestions from the many medical students over the past 17 years. Your positive reception has been an incredible encouragement for this book and the entire Case Files^® series. In this sixth edition of Case Files^®: Surgery, we have taken your comments and have rewritten and reformatted every chapter, simplifying and shortening the writing, emphasizing the high-yield principles, and tailoring the content to the clinical student level. In reviewing the topics, we deleted three cases to focus on surgical content and combined ulcerative colitis and Crohn disease for easier correlation. For the majority of cases, we have included a new section called Surgical Synopsis, which includes the relevant workup, main treatment, and indications for surgery for various conditions. New cases include Shock and Sepsis, Postoperative Fever and Intra-Abdominal Infection, Acute Respiratory Insufficiency and Mechanical Ventilation, Hemorrhagic Shock and Patient Safety, Penetrating Abdominal Trauma, Esophageal Perforation, Inflammatory Bowel Disease, Fascial Dehiscence and Incisional Hernia, Gallstone Disease, Periampullary Tumor, Tension Pneumothorax, Low Back Pain, Thyroid Nodules, Mediastinal Tumors and Thymomas, Carotid Artery Disease, Pediatric Surgical Conditions, and Chronic Kidney Disease and Transplant Medicine. We have also added entrustable professional activities (EPA) corresponding to the learning objectives. The multiple-choice questions have been carefully reviewed and rewritten to be consistent with the National Board and USMLE formats. By reading this sixth edition, we hope that you will continue to enjoy learning surgical management through the simulated clinical cases. It is certainly a privilege to be teachers for so many students, and it is with humility that we present this edition.