Killeen (Department of Laboratory Medicine and Pathology, University of Minnesota) offers an introduction to molecular pathology that encompasses both applied and theoretical knowledge. Writing in a readable style, he reviews the basic concepts of human molecular biology, explains principles of the most commonly used analytical methods, and discusses the molecular principles that underlie both inherited diseases and acquired genetic abnormalities that lead to cancer. Using common viral infections as examples, he applies these molecular methods to the detection of microbial pathogens, and highlights the importance of pharmacogenetics and identity testing in the clinical laboratory.