The intent of this chapter is to provide readers interested in toxicology a concise description of epidemiology, its bases, measures, study designs, and those considerations used to evaluate the quality of individual studies and effect measures. By the end of this chapter, the reader should be able to:

• Define epidemiology and discuss how it is utilized
• Discuss how disease is measured, the key measures of effect, and study designs used in epidemiology
• Distinguish between the various experimental, analytical, and descriptive study designs (e.g., randomized clinical trials, cohort studies, case-control studies, cross-sectional studies, ecologic studies, and case reports or case series)
• Define and discuss meta-analysis
• Understand how epidemiology results are interpreted, and how to evaluate study limitations due to confounding and bias
• Understand the basis for establishing causal relationships that identify human disease risk factor.

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