This book is a pocket-sized, practical introduction, and ready reference to focused ultrasound (USS) in the Emergency Department (ED). USS is a safe, rapid imaging technique. It is non-invasive and painless and it is used widely by radiologists, cardiologists (echocardiography) and obstetricians. However, it is only in recent years that its role has emerged in the field of Emergency Medicine. In this context, limited Emergency USS is used to answer very specific questions, such as the presence or absence of AAA (abdominal aortic aneurysm), or of free fluid (such as blood) in the abdomen after trauma. Unlike other imaging modalities (eg CT scan) it is a rapid technique that can 'come to the patient'. The book explains the indications for, and use of, limited USS. Importantly, it also explains its limitations.