This textbook introduces students to the basic concepts and methods used to measure and compare the expected benefits, risks and cost of preventive and therapeutic medical interventions. It provides an easily accessible overview of comparative effectiveness and its practical applications to daily medical decisions. The book includes learning objectives for each topic, definitions of key terms and topic summaries. Each chapter is written by a highly regarded academic and extensive reference is made throughout to other sources of literature where the interested reader can find further details.The book considers, among other topics, evidence based medicine and the role of comparative effectiveness research in the development of medical guidelines, bias and confounding, quality of life, randomized controlled trials, analyses of retrospective databases, screening and economic evaluation. The book is intended to serve as a “what is it?”, “why do we need it?” and “how does it or could it effect positive change in health care?” rather than just a “how to?” technical overview. As such, it provides an essential resource for both under- and post-graduate students in health sciences.