Appreciation of the differential diagnosis for a particular symptom or sign has been a pillar of the practice of general medicine for generations of doctors. This has never been more true than now, in the modern National Health Service (NHS) with its focus on patient safety. Keeping a broad differential in mind when approaching the new patient is often key to avoid pitfalls of tunnel vision in management. Equally, the importance of the differential diagnosis in undergraduate and postgraduate examinations cannot be understated. This book contains a series of lists of differential diagnoses for general medical presentations. We hope it will be of use for doctors wishing to refresh their memory with a quick reference guide, students of undergraduate medicine as well as postgraduate doctors in preparation for Membership of the Royal College of Physicians (MRCP) examinations. The best way to navigate the book is to identify the symptom or clinical feature required using the contents pages but the lists can be read in sequence for the general reader.