Microplate MUD/SF allows the practical identification and enumeration of intestinal enterococci in water, according to NF EN ISO 7899-1. The use of microtiter plates, with wells containing a specifically developed medium, was conceived for use in the analysis of several types of water, notably swimming and beach water in salt and fresh water, surface (still) water and post-treatment water. The method is applicable to all water samples, including those rich in suspended matter. For the enumeration of enterococci, the microtiter technique with MUD has been recognized as the most specific, precise, and rapid of all previously used methods. This technique represents an important evolution as regards to existing technologies for enterococci, which among the indicator microorganisms of fecal contamination, present a particular interest in water quality controls.