C57BL/6 (B6) and female BXSB mice were infected with 10 cercariae of Schistosoma mansoni per head in order to examine whether chronic parasite infection induced glomerulonephritis (GN) with polyclonal B-cell activation. Six months after the infection, mice were sacrificed and various immunological and histopathological examinations were performed. The following results were obtained. (1) Severe GN was induced in parasite-infected female BXSB mice. The renal changes were similar to those of male BXSB mice which spontaneously develop lupus-like GN. No substantial renal changes were observed in infected B6 mice. (2) Massive IgG and C3 deposits were found in capillary loops and also at the mesangial area of infected BXSB mice. No significant IC deposits were found in the kidney of infected B6 mice. (3) A high level of IC was detected in sera of some parasite-infected female BXSB mice, though no significant difference in the level of IC was found between infected and control mice. (4) Numbers of spleen IgG-producing cells were significantly increased in infected B6 mice. Infected female BXSB mice with splenomegaly showed higher numbers of IgGPC than uninfected mice, but there was no difference between the groups. These results suggest that genetic backgrounds played an important role in the development of lupus-like GN following the chronic infection of parasite-causing polyclonal B-cell activation.