Helicobacter pylori is very different from other Gram negative bacteria that inhabit the human gastroduodenal tract. Its success in adapting to colonise and persist in the stomach is reflected in key features such as unique chemical structure and architecture of lipopolysaccharide, sheathed flagella, genomic diversity, and potent urease activity. Strain diversity within the species is well established and so the challenge is to exploit variations in these features for developing relevant epidemiological typing methods.