In 1996, amendments to the Safe Drinking Water Act required the U.S. Centers for Disease Control and Prevention (CDC) and the U.S. Environmental Protection Agency (USEPA) to conduct studies to determine the occurrence of waterborne disease for at least five major communities or public water systems and prepare a report on the findings (Pontius 1997). The primary objective of the Water Evaluation Trial was to determine the incidence of gastrointestinal illness associated with consumption of drinking water meeting all federal and state treatment guidelines. The study was conducted by a team of epidemiologists at the University of California at Berkeley School of Public Health. To offset some of the criticisms of previous epidemiological studies, the Water Evaluation Trial used a randomized, triple-blinded, placebo-controlled, crossover, intervention design (Colford et al, 2002). The intervention tested household-level treatment of drinking water using a kitchen countertop device that treated tap water with ultraviolet light and microfiltration. Participating households were randomly assigned to two different groups. One group received the active device and the other received an identical-looking placebo (inactive) device. Half way through the study, "cross-over" occurred with the active devices replaced with inactive devices and the inactive devices replaced with active devices. The participants, the study staff, and the data analysis team were "blinded" (unaware of) to which group each household was assigned throughout the study. Blinding was necessary to reduce the likelihood of bias in reporting of disease and in the interpretation of the study results. The primary objective of the utility monitoring project was to characterize raw water, treatment plant, distribution, and household tap water quality with respect to microbes, water quality indictors, and physicochemical parameters so as to provide a context for interpreting the public health data generated by the epidemiology study (LeChevallier et al. 2004). Includes 11 references, figures.