Recently, experimentally Yersinia-induced arthritis in Lewis and SHR rats has been described as a potential animal model for analyzing the pathomechanism of reactive arthritis (Toivanen et al. 1986; Hill and Yu 1987). We could confirm that Lewis but not Fischer rats develop aseptic arthritis about 2 weeks after an intravenous inoculation of Yersinia enterocolitica, serotype 0:8 (Hill and Yu 1987). Moreover, we compared the antibody response to virulence-associated Yersinia antigens (Yops) of experimentally infected Lewis rats with that of Fischer rats using an enzyme-linked immunosorbent assay (ELISA) and immunoblotting. The ELISA results revealed a more rapid and vigorous specific IgG, IgA and IgM response for Lewis rats than for Fischer rats in the early state of infection. As demonstrated by immunoblotting, the IgG response was directed predominantly against the plasmid-encoded YopM, YopH, YopD and the V-antigen during the acute phase followed by antibodies against YopE and YadA. Although both rat strains seroconverted against this set of antigens, IgG antibodies to YadA were more prevalent and of higher titer in arthritis-susceptible rats compared to arthritis-resistant rats.