This study was designed to clarify the anti-nephritic effects of the saikosaponins that are contained in Bupleurum falcatum L. crude saikosaponin at 1.0 mg and 5.0 mg/kg, i.p. prevented urinary protein excretion and elevation of serum cholesterol content on the 10th day after the injection of anti-GBM serum. Moreover, crude saikosaponin at 1.0 mg and 5.0 mg/kg, i.p. significantly inhibited histopathological changes such as hypercellularity and adhesion. On the other hand, saikosaponin a (5.0 mg/kg, i.p.) and d (1.0 mg and 5.0 mg/kg, i.p.) also prevented urinary protein excretion, elevation of serum cholesterol content, and histopathological changes. In the second study, to clarify the anti-nephritic mechanisms of saikosaponins on this model, we investigated the effect of saikosaponins on platelet aggregation, release of corticosterone and reactive oxygen species scavengers activity. Crude saikosaponin and saikosaponin d significantly inhibited the increase in platelet aggregation, and saikosaponin d enhanced the serum and intra-adrenal corticosterone levels. Crude saikosaponin and saikosaponin a inhibited the decrease in activity of scavengers (SOD, catalase, glutathione peroxidase). These results indicate that saikosaponins were effective on this model, and anti-nephritic mechanisms of saikosaponins were party due to anti-platelet, corticosterone releasing and enhancing action on the activity of reactive oxygen species scavengers.