The conventional methods employed for detection of E. coli O157:H7 are laborious and time consuming. Existing methods lack the sensitivity to detect low levels of contamination that would be anticipated in untreated raw or finished tap water. This manuscript describes the development and multi-laboratory validation of procedures that employ immunological or molecular detection to enable detection of >0.05 CFU per mL of E. coli O157:H7 within a single day. The methods can conveniently dovetail into existing procedures for total coliform analyses or serve as stand-alone procedures. Employment of these procedures will allow utilities to accrue important epidemiological information and employ contingency measures to safeguard public health from this significant human pathogen. Includes 12 references, tables.