The book is aimed at medical students and others who wish to improve their diagnostic skills and interactions with patients. It describes how to justify diagnoses and management decisions verbally or in writing and clarifies what evidence is needed from research, and its statistical features. It provides senior doctors with a clear framework and examples help to teach trainees and students to approach diagnostic problems in a logical way and to effectively justify their opinions. It provides all doctors with practical help when dealing with problems outside their immediate field of expertise, especially general practitioners and those who are faced with unforeseen situations and emergencies.