Book excerpt: Despite diagnosis being the key feature of a physician's clinical performance, this is the first book that deals specifically with the topic. In recent years, however, considerable interest has been shown in this area and significant developments have occurred in two main areas: a) an awareness and increasing understanding of the critical role of clinical decision making in the process of diagnosis, and of the multiple factors that impact it, and b) a similar appreciation of the role of the healthcare system in supporting clinicians in their efforts to make accurate diagnoses. Although medicine has seen major gains in knowledge and technology over the last few decades, there is a consensus that the diagnostic failure rate remains in the order of 10-15%. This book provides an overview of the major issues in this area, in particular focusing on where the diagnostic process fails, and where improvements might be made.