Evidence-based medicine was developed to help physicians decide whether giving a patient a particular medicine is better than doing nothing at all, and occasionally to decide whether one medicinal product is better than another. Yet evidence-based medicine, as it is currently structured, provides only limited guidance for helping physicians decide what kind of care would be best for a particular patient at a particular point in time. To remedy this problem, epidemiologists must find ways to help physicians and laymen make use of epidemiological evidence, as well as experimental evidence. This book discusses the principles, implementation methods and effectiveness of evidence-based medicine.