To diagnose the abnormalities of coagulation-fibrinolysis in various renal diseases, we developed a new monoclonal antibody (D-D E72) against fibrin/fibrinogen degradation products D-dimer (FDP D-dimer) and established a highly sensitive enzyme-linked immunosorbent assay (ELISA) for its measurement. FDP D-dimer was assessed in 102 patients with various renal diseases, and the following results were obtained: 1. The mean level of urinary FPD D-dimer in 32 normal controls was 0.69 +/- 0.60 ng/ml (mean +/- SD). 2. The level of urinary FDP D-dimer was significantly higher in primary nephrotic syndrome group (NS), chronic renal failure group (CRF) and in the group of diabetic nephropathy (DM) than in the control group. However, no difference was observed in the level of urinary FDP D-dimer between non-nephrotic chronic glomerulonephritis group (CGN) and control group. 3. No significant correlation was revealed between D-dimer and urinary protein in CGN and NS groups. These results suggest that in addition to plasma filtration the urinary FDP D-dimer in NS, CRF and DM may be also related to abnormalities of secondary fibrinolysis in intra-glomerular fibrin deposits.