Method A describes a quantitative polymerase chain reaction (qPCR) procedure for the detection of DNA from enterococci bacteria in ambient water matrices based on the amplification and detection of a specific region of the large subunit ribosomal RNA gene (lsrRNA, 23S rRNA) from these organisms. The advantage of this method over currently accepted culture methods that require 24-48 hr to obtain results is its relative rapidity. Results can be obtained by this method in 3-4 hr, allowing same-day notifications of recreational water quality. While measurements of enterococci DNA by Method A and enterococci CFUs by culture methods such as EPA Method 1600 are performed for essentially the same purpose, i.e., to indicate fecal pollution, the results of these two approaches may not always be correlated with each other due to potential differences in the ratios of viable and non-viable bacteria in different water environments. Never-the-less, more recent epidemiological studies conducted at freshwater recreational beaches (Reference 17.3) have demonstrated similar or improved positive correlations between enterococci DNA measurements by this method and swimming-associated GI illness rates compared with those established for enterococci CFU measurements.