Three patients with clear cell renal carcinoma and one with another intrarenal malignancy were studied for the presence of glomerular localized immunoglobulins, complement components and tumor specific antigen and antibody by immunofluorescence. To determine the association and elucidate the pathogenic mechanisms involved in the relationship between tumors and glomerular deposits, antibody eluted from tumor tissue and renal glomeruli, cryoproteins, serum antibodies and rabbit antisera to tumor tissue were tested for specificity to antigen. The relationship between tumor antigens and the lipoprotein antigen localized in normal proximal tubular brush border (RTE) and the small bowel mucosa, was studied by immunofluorescence, absorption and blocking studies as well as complement fixation. Immunoglobulins and complement components were localized in the glomeruli and tumor membrane of all patients. Sera and glomerular fixed antibody from three patients with renal cell carcinoma localized to normal proximal tubular brush border and jejunal mucosa as well as to tumor membrane and the glomeruli and proximal tubules of all of these three patients. Anti RTE activity was also detected by complement fixation. Immunologic similarity between RTE and renal cell carcinoma antigen was confirmed by absorption studies. Furthermore, cryoprecipitable complexes of tumor antigen and specific antibody were isolated from the serum. The tumor antibody was immunologically similar to RTE. In the other case the rabbit anti-tumor antibody and the patient's serum fixed to the tumor membrane and kidney of the patient but did not show cross reactivity with the renal cell carcinoma or RTE. These studies suggest that the tumor antigen in renal cell carcinoma is similar to RTE and the glomerular deposits represent tumor antigen and antibody complexes. In addition these investigations support the hypothesis that tumor immune complexes are significant in the glomerular lesions, and that the origin of renal cell carcinoma is in the proximal tubule. The investigations also show that tumor antibodies are specific for tumors of the same morphological type but not for other tumors in the same tissue. Moreover, the renal glomerulus appears to be a chosen anatomic site for deposition of tumor antigens and antibodies and studies of the kidney may provide insight into the nature of tumor antigens and antibodies. Cryoprecipitation appears to be a valuable method in isolation of tumor complexes and characterization of tumor specific antigen and antibody.