The purpose of this study has been to identify antigen-antibody complexes by immunofluorescence in the kidneys of patients, especially those with leukemia and lymphoma, postmortem. The presence of such complexes may denote a chronic viral infection in which there is a minimal host response to virus resulting in the production of circulating complexes which are in antigen excess. In the early part of of this decade two kidneys with antigen-antibody complexes and coming from patients with acute leukemia stained postively with antisera to the cat leukemia virus. This has not been repeated, however, in other leukemic kidneys although a kidney from a patient with SLE stained positively with cat leukemia viral antiserum. Two kidneys from Uganda stained with antiserum to EBV, one from a patient with Burkitt's lymphoma and the other from a patient with Hodgkin's disease. Further six kidneys out of 11 from American patients both with and without tumors contained Ab to VCA in their acid eluates. These findins suggest that EBV-related immune complexes may be important in diseases other than Burkitt's lymphoma.