This article begins by discussing enteric viruses, specifically those that have been associated with waterborne disease outbreaks. Advances in molecular techniques for virus detection and identification are discussed, specifically polymerase chain reaction (PCR) which is a technique that copies a virus's genetic material (RNA or DNA) for detecting and identifying viruses in water samples. Techniques for sample collection, virus concentration, and cell culturing are discussed, along with coliphage assays. The article includes an inset that provides information on viruses, how they are spread, waterborne viral diseases, and four viruses on the U.S. Environmental Protection Agency's Contaminant Candidate List.