Three patients presenting typical nephrotic syndrome concurrent with gastric cancer are described. The carcinoma was moderately advanced and was histologically an adenocarcinoma in all cases. Morphologic examination of the renal biopsy revealed the characteristic changes of membranous nephropathy and typical subepithelial electron-dense deposits. The glomerular deposits were specifically stained with antihuman IgG and beta-1-c. The eluate of the glomeruli reacted specifically with the surface of the cancer cells from the same patient when studied by the immunofluorescent method. The eluate also reacted with the cancer cell extract as examined with the radioimmunodiffusion technique and with carcinoembryonic antigen (CEA) prepared by the method of Gold. Furthermore, the nephrotic syndrome completely remitted in 1 patient following surgical removal of the cancer. These bits of evidence indicate a possible role of a stomach cancer related antigen and/or CEA in the development of immune complex nephropathy in these patients.