Legionnaires' disease is caused by a type of bacteria called Legionella. CDC scientists have developed a real-time multiplex PCR assay for diagnosis and identification of Legionella strains. The assay consists of five sets of primers (targeting L. bozemanii, L. dumoffii, L. feeleii, L. longbeachae, or L. micdadei) and corresponding probes. Each probe is labeled with a different fluorophore which allows the detection of a particular strain in a single tube reaction. Using this assay format, the presence of any one of the five pathogenic non-pneumophila strains of Legionella can be detected rapidly from clinical or environmental samples. Rapid and sensitive identification enables initiation of appropriate antibiotic therapy and identification of the source of bacteria so that proper public health responses may occur.