The range of divergence of members of genus Campylobacter was analyzed by sequencing housekeeping genes. The utility of the dnaJ gene for identifying Campylobacter species was investigated by analyzing sequences of 34 reference strains, representing 16 species and three subspecies. The mean sequence similarity value of the dnaJ gene (66.98%) was significantly smaller than that of the 16S rRNA, rpoB and groEL genes (93.55%, 78.84% and 80.05%, respectively), indicating a high discriminatory power of the dnaJ gene. The dnaJ sequence variation within major independent pathogenic species of the genus Campylobacter was less than 3.8%. The application of the selected area of the dnaJ sequences for the species identification was confirmed by assigning 66 clinical isolates to the correct species of the genus Campylobacter. Our data indicates that simple analysis of dnaJ sequence is a new valuable tool for correct and rapid identification of Campylobacter species.