The polymerase chain reaction (PCR) as applied to the detection of Listeria monocytogenes in foods encompasses a variety of cell extraction, cell lysis, and DNA purification techniques. These techniques have been applied to foods directly and to enrichment broths with wide variations in sensitivity reported by numerous investigators. The selection of the specific gene for amplification of a selected sequence is also important in that some genes associated with pathogenicity have been found to be present in certain of the other species of Listeria. This review constitutes a detailed presentation of all such factors along with the tabulation of primer sequences, the genes from which they are derived, and the size of the amplified PCR products, in addition to descriptions of the use of nested primers and multiplex PCR.