Shiga toxin-producing Escherichia coli (STEC) have been identified as a worldwide cause of serious human gastrointestinal disease and the life-threatening hemolytic uremic syndrome. The most common serotype implicated is E. coli O157: H7, but infections involving various non-O157 serotypes have been found with increasing frequency in many countries. Food-borne outbreaks caused by STEC can affect large numbers of people and cause serious morbidity, making the bacteria one of the most important emerging pathogens. Because there is no specific treatment of the disease currently available, there is an urgent need for effective preventive measures based on a detailed understanding of the epidemiology of STEC infections. Such measures will also be dependent on the availability of rapid, sensitive, and simple procedures for the detection of the pathogens both in human samples and in samples of nonhuman origin such as food. This review summarizes the current knowledge on the epidemiology of STEC infection and presents a survey of laboratory methods currently available for diagnosis of STEC. Special attention is given to new diagnostic procedures for the less readily detectable non-O157 STEC strains and to simple procedures, usually based on commercially available kits, that can be used in routine clinical microbiological laboratories.