Yersinia enterocolitica may persist for prolonged periods of time in humans sometimes resulting in the development of reactive arthritis. To elucidate factors predisposing for persistence we developed animal models. In Lewis and Fischer rats, viable bacteria could be demonstrated for prolonged time and abscesses could be found in the liver, spleen and lungs. Splenic abscesses were observed for more than 20 weeks. Yersinia enterocolitica persisted in Lewis and Fischer rats, but only Lewis rats developed reactive arthritis. In Brown Norway rats abscesses developed early during infection but in contrast to the other strains disappeared after 3 weeks. Culture of homogenized abscess-containing tissue of all three rat strains yielded Yersiniae. Immunofluorescence studies of the abscesses showed diffuse staining inside the abscesses only, indicating the presence of Yersinia enterocolitica antigen. Brown Norway rats, in contrast to Lewis and Fischer rats, developed a different serological reaction pattern against Yersinia enterocolitica antigens and this correlated with the disappearance of the abscesses.