Book excerpt: There are at least three ways in which a public health program or policy may not reach stated goals for success: 1) Choosing an intervention approach whose effectiveness is not established in the scientific literature; 2) Selecting a potentially effective program or policy yet achieving only weak, incomplete implementation or "reach," thereby failing to attain objectives; 3) Conducting an inadequate or incorrect evaluation that results in a lack of generalizable knowledge on the effectiveness of a program or policy; and 4) Paying inadequate attention to adapting an intervention to the population and context of interest To enhance evidence-based practice, this book addresses all four possibilities and attempts to provide practical guidance on how to choose, carry out, and evaluate evidence-based programs and policies in public health settings. It also begins to address a fifth, overarching need for a highly trained public health workforce. This book deals not only with finding and using scientific evidence, but also with implementation and evaluation of interventions that generate new evidence on effectiveness. Because all these topics are broad and require multi-disciplinary skills and perspectives, each chapter covers the basic issues and provides multiple examples to illustrate important concepts. In addition, each chapter provides links to the diverse literature and selected websites for readers wanting more detailed information. An indispensable volume for professionals, students, and researchers in the public health sciences and preventative medicine, this new and updated edition of Evidence-Based Public Health aims to bridge research and evidence with policies and the practice of public health.