Autoantibody formation and lymphocytes proliferative response to tubular basement membrane (TBM) antigen were examined to clarify the pathogenesis of gold nephropathy, in rheumatoid arthritis patients. The existence of tubulopathy was ascertained by urine protein analysis, electrophoresis and urine TBM antigen titration. Circulating antibody to human TBM antigen titrated by enzyme immunoassay was significantly elevated in patients with gold tubulopathy, and mitogenic stimulation with TBM antigen of peripheral lymphocytes specifically responded in the early stage after receiving gold, but then clearly decreased after the cessation of gold. But, when the lymphocytes had been passed through a nylon wool column, the reaction was remarkably high even in the later stage after receiving gold, suggesting that another suppressive population of lymphocytes became trapped in the nylon wool column. This evidence suggests that gold compounds definitely act as initiating and promoting agents, and the development of tubular disorders induced by gold are likely related to the cellular recognition of effector T cells to the TBM antigen, following the strong effect of gold on the cellular immune system.