This chapter should give the reader a good idea of what this book is about. In one sentence, this book introduces the reader to the design and analysis of medical test accuracy, with emphasis on a Bayesian analysis. A Bayesian approach is taken where the foundation is based on Bayes theorem, and all inferences are expressed as posterior distributions of the relevant parameters. WinBUGS is the software that will execute Bayesian inferences for medical test accuracy and the associated code is labeled in the book and also appears on the author’s blog. In what follows, I will carefully describe the contents of each chapter, so that the reader will know what to expect.