The chapter acknowledges the contributions of various individuals and groups to the research, including members of the Capechi laboratory's tissue culture support group and animal care facility, as well as specific assistance from L. Oswald, P. Reid, D. Lim, and R. Begarian. J.M.G. was supported by the Dee Fellowship and a NIH Genetics Training Grant. The correspondence and requests for materials should be directed to M.R.C. The genome sequence of *Campylobacter jejuni* NCTC11168, a leading cause of food-borne diarrhea and Guillain–Barré syndrome, is reported. The genome is 1,641,481 base pairs long, encoding 1,654 proteins and 54 stable RNA species. Notably, the genome lacks insertion sequences, phage-associated sequences, and repetitive DNA. The presence of hypervariable sequences, particularly in genes involved in surface structure biosynthesis, is highlighted. These sequences may play a role in the survival strategy of *C. jejuni*. The genome also lacks many DNA repair genes and has a unique organization of genes into operons or clusters. The high rate of variation in homopolymeric tracts suggests rapid phase variation, which could be important for colonization and immune evasion. The study also discusses the lack of similarity between *C. jejuni* and *Helicobacter pylori* in terms of gene content and regulatory systems, indicating significant evolutionary divergence despite their close phylogenetic relationship.The chapter acknowledges the contributions of various individuals and groups to the research, including members of the Capechi laboratory's tissue culture support group and animal care facility, as well as specific assistance from L. Oswald, P. Reid, D. Lim, and R. Begarian. J.M.G. was supported by the Dee Fellowship and a NIH Genetics Training Grant. The correspondence and requests for materials should be directed to M.R.C. The genome sequence of *Campylobacter jejuni* NCTC11168, a leading cause of food-borne diarrhea and Guillain–Barré syndrome, is reported. The genome is 1,641,481 base pairs long, encoding 1,654 proteins and 54 stable RNA species. Notably, the genome lacks insertion sequences, phage-associated sequences, and repetitive DNA. The presence of hypervariable sequences, particularly in genes involved in surface structure biosynthesis, is highlighted. These sequences may play a role in the survival strategy of *C. jejuni*. The genome also lacks many DNA repair genes and has a unique organization of genes into operons or clusters. The high rate of variation in homopolymeric tracts suggests rapid phase variation, which could be important for colonization and immune evasion. The study also discusses the lack of similarity between *C. jejuni* and *Helicobacter pylori* in terms of gene content and regulatory systems, indicating significant evolutionary divergence despite their close phylogenetic relationship.