Enterococci spp. is an indicator microorganism routinely tested in Europe for water quality. The current ISO method for the detection and enumeration of intestinal enterococci (method 7899-2) is a 48-hour membrane filtration method using Slanetz & Bartley medium followed by a two-hour confirmation procedure using bile-esculin-azide agar. Enterolert-E (IDEXX Laboratories, Inc. Westbrook, ME, USA) is based on IDEXX's Define Substrate Technology for detecting Enterococci spp. in water samples. This medium when used with IDEXX's Quanti-tray or Quanti-tray/2000 provides quantitative confirmatory results in 24 hours. Includes 2 references, figure.