Renal lesions at the chronic phase of MHC class-II-disparate graft-versus-host reaction (GVHR) were examined. To induce GVHR, C57BL/6 (B6) spleen cells were injected twice into either (B6xbml2)F1 (class-II-disparate), (B6xbml)F1 (class-I-disparate) or (bmlxbml2)Fl mice (class-I+II-disparate). for comparison, (C57BL/10xDBA/2)F1 (BDF1) mice injected with DBA/2 spleen cells were also used.(B6xbml2)F1 and BDF1 recipients showed marked elevation of anti-DNA antibodies, circulating immune complexes (CIC) and the number of immunoglobulin producing cells (IgPC). At 20 weeks after cell injection, severe immune complex glomerulonephritis (ICGN) was observed in (B6xbml2)F1 recipients, but was far less severe in (bmlxbml2)F1 recipients and was not observed in (B6xbml)F1 recipients. ICGN was also observed in BDF1 recipients at 12 weeks after cell injection. By immunofluorescent microscopy, IC deposition was detected along the capillary loops and also in the mesangial area in (B6xbml2)F1 recipients, while BDF1 recipients showed only a capillary pattern. By light microscopy, the renal lesion of (B6xbml2)Fl recipients appeared similar to those of BDF1 recipients. Histologically, (B6xbml2)F1 recipients serve as a good model for lupus glomerulonephritis induced by class-II-disparate GVHR.