We appreciate all the kind remarks and suggestions from the many medical students over the past four years. Your positive reception has been an incredible encouragement, especially in light of the short life of the Case Files^® series. In this fifth edition of Case Files^®: Surgery, the basic format of the book has been retained. Improvements were made by updating many of the chapters, with five completely rewritten cases: Breast Cancer Risk and Surveillance, Colon Cancer, Thyroid Mass, Pheochromocytoma, and Hemorrhage and Hypotension. We reviewed the clinical scenarios with the intent on improving them; however, we found that their real-life presentations patterned after actual clinical experience remained accurate and instructive. The multiple-choice questions have been carefully reviewed and rewritten to ensure that they comply with the National Board and USMLE formats. By reading this fifth edition, we hope that you will continue to enjoy learning surgical management through the simulated clinical cases. It is certainly a privilege to be a teacher for so many students, and it is with humility that we present this edition.