Detection and identification of fastidious pathogenic bacteria have traditionally presented an obstacle to the clinical and laboratory microbiologist. The diagnosis of disease caused by these bacteria is often empiric relying on clinical observations or indirect laboratory tests. Recently, a technique called broad-range polymerase chain reaction (PCR) has been integrated into studies designed to detect and identify previously uncharacterized bacterial pathogens. By using regions of the bacterial 16S ribosomal RNA (rRNA) gene that are highly conserved to prime synthesis of the remainder of this gene, PCR amplification can be performed directly from clinical samples which may contain small numbers of bacteria. The resulting PCR-amplified DNA can be sequenced to identify variable regions of the 16S rRNA gene that are bacteria-specific. This technique has proven valuable in identifying new fastidious bacterial pathogens that have resisted detection and identification by traditional microbiological methods.