This timely book presents the epidemiologic methods that can be used to determine when screening procedures are indicated, focusing on how to describe and measure changes in the natural history of disease brought on by early treatment, lead time, and prognostic selection. The author explains how to assess the usefulness of screening in reducing morbidity and mortality, and provides thorough descriptions of the experimental and case-control approaches. "An intelligent account of the role screening can play in detecting disease . . . replete with figures and tables with examples of the pros and cons of different screening tests." --Journal of the American Medical Association