This is a self-instructional manual on the interpretation and use of epidemiologic data that deals with the basic concepts and skills needed for appraising published reports or study findings. Applications in clinical medicine, public health, community medicine, and research are presented. The numerous changes in this edition include the addition of a section on questions to be asked before deciding to apply study results in practice, discussions of new topics (Cox proportional hazards regression, qualitative studies, ROC curves), and fresh examples.