Contamination of public drinking water and the resulting health consequences have been documented for several centuries. When such occurrences take place, scientists and public health officials require water distribution systems analysis to identify the source(s), duration, and frequency of the contamination. This information is then used to characterize and quantify the public's exposure to contaminants in drinking water. Typically, studies conducted by health scientists and epidemiologists related to exposure to water-distribution system contamination are retrospective in nature- reconstructing the contamination event(s) in order to document exposure and health impacts. Four historical cases will be used to illustrate the application of water-distribution systems analysis for supporting public health investigations: (1) the 1854 cholera outbreak in London, England, (2) childhood leukemia investigation, Woburn, Massachusetts, (3) childhood cancer cluster investigation, Dover Township (Toms River), New Jersey, and (4) volatile organic compound contamination of drinking water, U.S. Marine Corps Base Camp Lejeune, North Carolina. These four historical and high-profile public health cases demonstrate the contributions of water-distribution systems analysis to epidemiological investigations and to quantifying the public's exposure to contaminated drinking water.