The (NZB X NZW)F1 mouse is recognized as an important animal model of the human disease systemic lupus erythematosus (SLE). Groups of NZB/W F1 mice were treated either with IFN-gamma or with PBS. The results demonstrate that IFN-treated animals have accelerated development of fatal immune complex glomerulonephritis relative to age-matched controls. On the other hand, administration of mAbs specific for IFN- gamma to such mice from 4 to 7 mo of age resulted in significant remission. Development of both proteinuria and anti-DNA antibodies were delayed and survival at 11 mo was increased from less than 20% to 95% in treated mice relative to controls (p less than or equal to 0.001). These findings may have therapeutic implications for the treatment of SLE.