Renal tissue from 71 patients with membranous glomerulonephritis was studied for the presence of renal tubular antigens in glomerular deposits by indirect immunofluorescence, using a rabbit antiserum prepared against a human renal tubular antigen, Fx1A. The rabbit antiserum was reactive with antigens normally present in the brush border regions of proximal tubules of human and rat kidneys and in the glomerular deposits of rats with Heymann nephritis. However, renal tubular antigens were not detectable in any of the cases of human membranous glomerulonephritis, either before or after partial elution of immunoglobuhns from glomeruh. Eluates of renal tissue from 5 of the patients and sera from 6 patients did not contain antibodies against renal tubular antigens demonstrable by immunofluorescence. These findings fail to provide evidence for a role of renal tubular antigens in human membranous glomerulonephritis.