We investigated the antinephritic effect of TJ-8014, in comparison to dipyridamole, on accelerated passive Heymann nephritis in rats. TJ-8014 (4.0 g/kg/day, p.o.) given from the heterologous phase (from the day of injection of the antiserum against Fx1A) markedly inhibited the urinary protein excretion and the elevation of plasma cholesterol levels as well as glomerular histopathological changes. When the treatment was started from the autologous phase (from the 22nd day) after proteinuria was fully developed, TJ-8014 also showed a beneficial effect. Dipyridamole (0.4 g/kg/day, p.o.) had no effect when the treatment was started either from the heterologous or autologous phase. TJ-8014 decreased glomerular rat IgG and rat C3 deposits, although it affected neither the plasma antibody titer against rabbit gamma-globulin nor the plasma complement level. TJ-8014 markedly prevented the reduction of plasma and adrenal corticosterone level as well as the reduction of renal blood flow of rats with nephritis. These results suggest that TJ-8014 may be a useful drug against idiopathic membranous nephropathy and the beneficial effect of this drug may be caused by the elimination of glomerular immune deposits and C3 through the increase in renal blood flow related to the enhanced release of adrenal corticosterone.