Broiler carcasses (n=325) were sampled at three sites along the processing line (prescalding, prechilling, and postchilling) in a commercial poultry processing plant during five plant visits from August to October 2004. Pulsed-field gel electrophoresis (PFGE) was used to determine the genomic fingerprints of Camospylobacter coli (n=27), Campylobacter jejuni (n=188), Arcobacter butzleri (n=138), Arcobacter cryaerophilus 1A (n=4), and A. cryaerophilus 1B (n=31) with the restriction enzymes SmaI and KpnI for Campylobacter and Arcobacter, respectively. Campylobacter species were subtyped by the Centers for Disease Control and Prevention PulseNet 24-h standardized protocol for C. jejuni. A modification of this protocol with a different restriction endonuclease (KpnI) and different electrophoresis running conditions produced the best separation of restriction fragment patterns for Arcobacter species. Both unique and common PFGE types of Arcobacter and Campylobacter strains were identified. A total of 32.8% (57 of 174) of the Arcobacter isolates had unique PFGE profiles, whereas only 2.3% (5 of 215) of the Campylobacter isolates belonged to this category. The remaining Arcobacter strains were distributed among 25 common PFGE types; only eight common Campylobacter PFGE types were observed. Cluster analysis showed no associations among the common PFGE types for either genus. Each of the eight common Campylobacter types consisted entirely of isolates from one sampling day, whereas more than half of the common Arcobacter types contained isolates from different sampling days. Our results demonstrate far greater genetic diversity for Arcobacter than for Campylobacter and suggest that the Campylobacter types are specific to individual flocks of birds processed on each sampling day.