I have been deeply amazed and grateful to see how the Case Files^® books have been so well received, and have helped students to learn more effectively. In the 13 short years since Case Files^®: Obstetrics and Gynecology first made it in print, the series has now multiplied to span most of the clinical and basic science disciplines, and been translated into nearly 20 foreign languages. Numerous students have sent encouraging remarks about the changes in the fourth edition, which divided up into Obstetrics in the first half, and Gynecology in the second half to be more “user-friendly” during the clerkship since most students have their rotation divided in those two categories. In this fifth edition, we have retained the grouping of related cases closer together to allow students to use information from one case to reinforce principles to another case, and cross-referenced-related cases. Although space is always a premium, we have also retained and expanded Section III which is a collection of strategic questions that can be used for review, but also to tie in the principles from the cases. Questions have been improved to better reflect the USMLE format, and explanations have been expanded to help the student understand the mechanisms and the reason that the other choices are incorrect. Two completely new cases (Sexual Abuse/Intimate Partner Violence, and Chronic Pelvic Pain) have been written. Updated or new sections include cervical cytology screening, contraception, labor management, hypertension in pregnancy, fetal assessment, and ovarian cancer. This fifth edition has been a collaborative work with my wonderful coauthors and contributors, and with the suggestions from five generations of students. Truly, the enthusiastic encouragement from students throughout not just the United States but worldwide provides me with the inspiration and energy to continue to write. It is thus with humility that I offer my sincere thanks to students everywhere ... for without students, how can a teacher teach?