Written for physicians, medical students, and other health care professionals, this text explains epidemiologic concepts clearly and simpy, illustrating them with clinically relevant case studies. It bridges the gap between clinicians and epidemiologists, showing the relatioship between individual patients and the groups to which they belong, in epidemiologists' eyes. It also examines the relevance of epidemiology to the study of socially and politically important issues, such as changing health care systems and environmental hazards.