This Technical Specification specifies a method for the detection and quantification of Legionella spp. and L. pneumophila using a quantitative polymerase chain reaction (qPCR). It specifies general methodological requirements, performance evaluation requirements, and quality control requirements. Technical details specified in this Technical Specification are given for information only. Any other technical solutions complying with the performance requirements are suitable. NOTE For performance requirements, see Clause 10. This Technical Specification is intended to be applied in the bacteriological investigation of all types of water (both hot and cold), unless the nature and/or content of suspended matter and/or accompanying flora interfere with the determination. This interference can result in an adverse effect on both the detection limit and the quantification limit. The results are expressed as the number of genome units of Legionella spp. and/or L. pneumophila per litre of sample. The method described in this Technical Specification is applicable to all types of water. However, some additives, e.g. chemicals used for water treatment, can interfere with and/or affect the sensitivity of the method. The qPCR methods do not give any information about live or dead cells.