The inflammatory response in the mouse stomach was evaluated as a means of distinguishing different non-pylori Helicobacter (H.) strains in terms of virulence. Mice of four strains (BALB/c, SJL, C57BL/6 and CFW) were infected intragastrically with four bacterial strains (H. felis ATCC 49179 and CCUG 37471, H. bizzozeronii and H. salomonis). The animals were killed for gastric examination at 3, 9 or 16 weeks post-inoculation. H. salomonis could not be detected by the polymerase chain reaction, but the other three organisms were detected in all stomach samples at all timepoints. SJL mice consistently showed particularly severe gastric inflammation regardless of bacterial strain. Lymphocytes and occasionally neutrophils were seen in submucosa and lamina propria mucosae. BALB/c mice showed the least severe inflammatory changes. H. bizzozeronii differed from the two H. felis strains in producing less striking pathological changes in mice. Of the two H. felis strains, ATCC 49179 produced the more severe inflammatory changes in SJL mice.