Epidemiological methods are crucial to extract as much valid information as possible from human metal exposures. Thus, modern epidemiological approaches have elucidated human health effects that were not apparent in the past. At the same time, metal toxicology has served as a useful arena for testing and further refining methods for study design and data analysis. In contrast to most organic compounds, metals are not broken down, and many of them are retained in the body for long periods, thereby facilitating exposure assessment. In conjunction with the use of inexpensive metal analytical methods, exposures can be characterized from the analysis of blood, urine, and other biological samples. The availability of multiple approaches for exposure assessment allows a calculation of the total imprecision, thus paving the way for adjustment for measurement error. Likewise, due to their propensity to cause chronic or delayed toxicity, epidemiological studies of metal toxicity have focused on a wide variety of organ systems, subtle effects as well as mortality, and differences in susceptibility. Toxic metals often serve as paradigms of environmental and occupational toxicity. For these reasons, this chapter highlights the fields within epidemiology that are most relevant to toxic metals and discusses where these substances serve to illustrate important epidemiological concepts. Chapter sections include subjects such as epidemiological terms, study design, study population, exposure assessment, assessment of effects, data analysis, and assessment of benchmark dose, and inference.