The VanderbiltDDx Case Simulator (“App”) helps users to practice and refine their diagnostic skills. It creates realistic, fun, easy-to-evaluate adult (age 16-75+) patient cases. The intended audience includes medical, nursing, physician assistant, and other health professional students; physicians undergoing residency and fellowship training; nurses in advanced practice training; and practicing health professionals. The App generates cases using a large, evidence-based, literature- derived knowledge base (630+ disorders seen by internists, 4500+ findings). To construct each simulated case, the App randomly selects logically consistent findings based on how often the literature indicates the findings occur in patients with the targeted disorder. Vanderbilt is distributing the App free-of-charge via its Portal on the App Store for use in clinical education. The App, once installed, is self-contained on users’ iOS devices. It does not transmit any information about the user or use of the App. Typical App workflow is as follows: (1) User sets difficulty level/clinical focus; starts random simulated case. (2) App randomly selects a disorder and displays initial set of findings. (3) User, via App, elicits additional findings (i.e., works up case). (4) App shows potential diagnoses matching known case findings. (5) App indicates how well the known case findings support or refute selected hypotheses. User identifies their three most favored hypotheses. (6) User rates “strength of evidence” supporting top three hypotheses. (7) App discloses answer and assesses user’s performance. (8) User gains knowledge by reviewing disorder-related information. Users can provide feedback to the development team regarding bugs and suggestions to make the App more useful. Send such comments to: [email protected] The App’s primary developer, Randolph A. Miller, MD, is Professor Emeritus of Biomedical Informatics and Medicine at Vanderbilt University School of Medicine. He was the founding Chair of Vanderbilt’s Department of Biomedical Informatics and is a Past President of both the American Medical Informatics Association (AMIA), and the American College of Medical Informatics.