In order to clarify whether TNF inhibitory activity in the urine of glomerulonephritis (GN) patients depends on the existence of TNF inhibitors/soluble TNF receptors, we purified two types of TNF inhibitors from the urine of chronic renal failure (CRF) with GN patient. Using four steps of chromatography (anion exchange chromatography, preparative reverse phase chromatography, TNF affinity chromatography, analytical reverse phase chromatography), two types of 99% pure TNF inhibitors were purified. Amino terminal amino acid sequence revealed that one inhibitor was identical to soluble TNF receptor, p55, however, the other was homologous but not identical to soluble TNF receptor, p75. Our experiments demonstrated that TNF inhibitory activity in the urine of CRF patients depended partly on the existence of soluble TNF receptors in the urine.