Now in its fourth edition, Rational Diagnosis and Treatment: Evidence-Based Clinical Decision-Making is a unique book to look at evidence-based medicine and the difficulty of applying evidence from group studies to individual patients. The book analyses the successive stages of the decision process and deals with topics such as the examination of the patient, the reliability of clinical data, the logic of diagnosis, the fallacies of uncontrolled therapeutic experience and the need for randomised clinical trials and meta-analyses. It is the main theme of the book that, whenever possible, clinical decisions must be based on the evidence from clinical research, but the authors also explain the pitfalls of such research and the problems involved in applying evidence from groups of patients to the individual patient. For this new edition, the sections on placebo and meta-analysis and on alternative medicine have been thoroughly updated, and there is more focus on insufficient reporting of harms of interventions. The sections on different research designs describe advantages and limitations, and the increased medicalisation and the effects of cancer screening on health people are noted. A section on academic freedom when clinicians collaborate with industry and ghost authors is added. This essential reference work integrates the science and statistical approach of evidence-based medicine with the art and humanism of medical practice; distinguishing between data, sets of data, knowledge and wisdom, and their application. Such an intellectually challenging book is ideal for both medical students and doctors who require theoretical and practical clinical skills to help ensure that they apply theory in practice.