Three inbred strains of mice were identified which demonstrated different susceptibilities to induction of immune complex glomerulonephritis (ICGN) despite sharing the same major histocompatibility complex haplotype (H-2k). Groups of mice from each of these three strains, B10.BR, CBA and C3H/HeJ, were injected with one of two different dose schedules of horse apoferritin (HAF) for 4 weeks, after which glomerular morphology, immunoglobulin deposition, and serum anti-HAF antibody levels were examined. With either dose schedule, only those mice which demonstrated a high level antibody response developed ICGN and glomerular immunoglobulin deposition. These results suggest that susceptibility to ICGN in this model is related to the level of antigen exposure and to the magnitude of the antibody response, which is not under strict control of the major histocompatibility complex.