Helicobacter pylori has been found to cause chronic active gastritis and has been identified as a primary etiologic factor in duodenal and gastric ulcer and non-ulcer dyspepsia in humans. It has also been implicated as a facfor in the development of gastric lymphoma and adenocarcinoma. Since these discoveries, greater attention has been paid to the potenfial significance of similar spiral shaped gastric bacteria that have been seen for many years in gastric biopsies of veterinary patients. Helicobacter organisms have been identified in many species of animals including humans, dogs, cats, rodents, pigs, ferrets, nonhuman primates and many wild carnivores. Many different species of Helicobacter have been identified, and each species differs in its host range and pathogenicity (Table 1).