Presentation of medical information in a concise, evidence-based, and credible format remains a constant challenge. The vast amount of available knowledge necessitates a committed effort by editors and authors to highlight the new developments while reinforcing the core principles of medicine. To assist physicians in this ongoing challenge, the Department of Internal Medicine at Mayo Clinic remains committed to providing continuing professional development to physicians in a timely manner. Mayo Clinic Internal Medicine Board Review, 9th edition, is designed to meet the needs of physicians who are in training and practicing clinicians by updating their knowledge in internal medicine and preparing them for the American Board of Internal Medicine certification and maintenance-of-certification examinations in internal medicine. The book is divided into subspecialty topics, and each chapter or subsection of a chapter is written by authors with wide clinical expertise in the area. Bulleted items address typical clinical scenarios. These scenarios emphasize 2 key points: the diagnosis of diseases by general internists and subspecialists in internal medicine and the predominance of pharmacologic management. Pharmacy review tables list the indications for and adverse effects of drugs and drug-drug interactions, knowledge that is of paramount importance for practicing physicians.