Rare "paraneoplastic nephropathies" are associated with a wide variety of human tumors. Little is known about the pathogenetical background. To our knowledge no systematic study about the association of potentially "immunogenic" renal cell cancer (RCC) and "paraneoplastic nephropathy" has been published so far. An immunohistochemical analysis of native kidneys and a nephrological follow up of 60 patients with renal cell cancer (RCC) treated at the Department of Urology, medical University, Pécs (Hungary) between 1993-1998 has been performed. Cellular and humoral immunity was analysed by immunohistochemistry. Clinical/laboratory parameters of the patients with tumor associated nephropathy were pre- and postoperatively registered. Eleven IgA-nephropathy (IgA-NP) and 5 focal segmental glomerulosclerosis (FSGS), manifested in preoperative clinical signs in 11 out of 16 cases were found. Clinical symptoms disappeared in 6 out of 8 IgA-NP patients by tumor nephrectomy in a follow up of 38.7 (18-51) months. Eleven out of 16 tumors were stained with the identical anti human immunoglobulin (IgA or IgM) present in the glomerular immune complexes. The RCC-associated VHL (von Hippel-Lindau) protein was detectable in 3 out of 8 IgA-NP patients as an antigen component of their nephritogenic immune complexes. Tumor infiltrating lymphocytes (TIL) considered as a local sign of cellular tumor immunity were more frequently present in tumors associated with nephropathy than without it (69% vs 25%). Pathogenetic correlation between the tumor immunity in renal cell carcinoma and "paraneoplastic IgA-nephropathy" has been demonstrated in some of the cases. Tumor nephrectomy excluding the need of post-operative single kidney biopsies should be a safe tool in the differential diagnosis of tumor-associated nephrological conditions.