Campylobacter-like organism was isolated from the ilea of normal hamsters. The organism was isolated from an ileal homogenate which was passed through a filter (0.65-,um pore size) and cultured on blood-agar plates in a microaerophilic atmosphere at 37°C. Pinpoint translucent colonies were first observed after 120 h of incubation. The isolated organism measured 2.0 to 3.5 ,um in length (excluding flagella) by 0.17 to 0.25 uLm in width and typically had a single terminal sheathed flagellum. The organism was oxidase, catalase, and urease positive, reduced nitrates, and was susceptible to nalidixic acid (30-,g disk) and resistant to cephalothin (30-,ug disk). Unlike Campylobacter pylori subsp. mustelae, this organism did not hydrolyze indoxylacetate. Immunofluorescence studies with a Campylobacter species-specific monoclonal antibody (8322-2E6) revealed the presence of numerous positively stained organisms within the crypt epithelial cells of the hamsters from which this organism was isolated. The role of this organism in the pathogenesis of proliferative ileitis in hamsters is uncertain, as is the taxonomic relationship of this organism to other members of the genus Campylobacter.