The nucleotide sequence of a region located downstream of the Listeria monocytogenes flagellin gene, flaA, has been determined. DNA sequence analysis revealed the presence of two open reading frames with a potential to encode polypeptides of 13.1 and 68.7 kDa, respectively. The deduced polypeptides show a high degree of identity to the chemotactic proteins, CheY and CheA, respectively, from Bacillus subtilis and Escherichia coli. Moreover, significant features of CheY and CheA are conserved in the L. monocytogenes homologues. The high degree of conservation suggests that the polypeptides are involved in signal transduction controlling chemotaxis in L. monocytogenes and consequently the putative genes are named cheY and cheA. Northern blot and primer extension analysis suggested that cheY and cheA are transcribed as a bicistronic unit and that the transcription is thermoregulated.