Introduction -- The dynamics of disease transmission -- Measuring the occurrence of disease: I. Morbidity -- Measuring the occurrence of disease: II. Mortality -- Assessing the validity and reliability of diagnostic and screening tests -- The natural history of disease: ways of expressing prognosis -- Assessing the efficacy of preventive and therapeutic measures: randomized trials -- Randomized trials: some further issues -- Cohort studies -- Case-control studies and other study designs -- Estimating risk: is there an association? -- More on risk: estimating the potential for prevention -- A pause for review: comparing cohort and case-control studies -- From association to causation: deriving inferences from epidemiologic studies -- More on causal inferences: bias, confounding, and interaction -- 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.