Introduction -- The dynamics of disease transmission -- Measuring the occurrence of disease: I. Morbidity -- II. Mortality / Measuring the occurrence of disease -- Assessing the validity and reliability of diagnostic and screening tests -- ways of expressing prognosis / The natural history of disease -- randomized trials / Assessing the efficacy of preventive and therapeutic measures -- some further issues / Randomized trials -- Cohort studies -- Case-control studies and other study designs -- is there an association?. More on risk: estimating the potential for prevention / Estimating risk -- comparing cohort and case-control studies / A pause for review -- deriving inferences from epidemiologic studies / From association to causation -- bias, confounding, and interaction / More on causal inferences -- Identifying the roles of genetic and environmental factors in disease causation -- Using epidemiology to evaluate health services -- The epidemiologic approach to evaluating screening programs -- Epidemiology and public policy -- Ethical and professional issues in epidemiology.