Prevalence of Helicobacter infection in pet dogs and positive relations between the presence of Helicobacter app. and gastritis were studied. Twenty-one dogs, which died of various disease, were referred from three animal hospitals and necropsied. Upon histopathological examination, Helicobacter-like organisms (HLO) were observed only in the gastric mucosa of 5 (23.5%) out of the 21 stomachs. The bacteria mainly colonized in the mucus, gastric pits, and the lumen of gastric glands. Regardless of HLO infection, there was mild to moderate lymphocytic infiltration in fundic and pyloric mucosa. Average gastritis scores of the group infected with HLO were 1.250${pm}$0.214 and 1.833${pm}$0.167 in the fundic and pyloric mucosa, whereas those of uninfected group were 1.000${pm}$0.165 and 1.625${pm}$0.239, respectively. Accordingly, we concluded that no association exists between HLO infection and gastritis.