This part of ISO 7899 specifies a method for the detection and enumeration of intestinal enterococci in water by membrane filtration. This part of ISO 7899 is especially intended for examination of drinking water, water from swimming pools and other disinfected or clean waters. Nevertheless, the method can be applied to all types of water, except when a large amount of suspended matter or many interfering microorganisms are present. It is particularly suitable for the examination of large volumes of water containing only a few intestinal enterococci.