The renal biopsies of 30 patients with rheumatoid arthritis and clinical evidence of renal disease were reviewed; only patients in whom the intravenous pyelogram was normal were subjected to biopsy, thus excluding those with papillary necrosis and chronic pyelonephritis. Tissue was studied by light, electron and immunofluorescence microscopy. There were 13 cases of mesangial change, 9 of membranous glomerulonephritis, 4 of tubulointerstitial change, 2 cases of focal segmental glomerulosclerosis, 1 case of amyloid and 1 of diffuse proliferative glomerulonephritis with crescents. All 9 patients with membranous glomerulonephritis but only 6 of 13 with mesangial change had received gold or penicillamine. We found no evidence of "glomerulitis" or of a rheumatoid vasculitis.