The phylogeny of twelve Campylobacter species was determined based on partial (1020-bp) gyrB gene sequences. Methods have been described for detection and speciation of Campylobacter, including 16S rRNA sequence analysis. However, gyrB provides a better resolution than the 16S rDNA gene for Campylobacter species with interspecies sequence similarities ranging from 58.3 to 89.2% compared to those reported for the 16S rRNA gene (ranging from 89 to 99%). A universal primer set, designed to amplify a 900-bp fragment of the gyrB gene in Campylobacter spp., was developed and used for PCR-RFLP of 19 strains representing twelve Campylobacter species and resulted in unique digest patterns for all twelve Campylobacter species PCR assays for amplification of regions of the gyrB gene specific for each Campylobacter species were also developed. Using these PCR and PCR-RFLP methods results in unambiguous identification of the majority of Campylobacter species.