In order to clarify the abnormalities of the coagulation and fibrinolysis system in patients with various renal diseases, we produced a new monoclonal antibody for FDP (fibrin/fibrinogen degradation product) D-dimer (D-D E72). We also established a new highly sensitive method of enzyme-linked immunosorbent assay (ELISA) for urinary FDP D-dimer using this monoclonal antibody. The urine from 110, patients with various renal diseases was investigated for the FDP D-dimer. The results are summarized as follows: 1) Urinary FDP D-dimer in normal subjects was 0.69 +/- 0.60 ng/ml. 2) The level of urinary FDP D-dimer in patients with primary nephrotic syndrome and in patients with chronic renal failure was significantly higher than that of normal subjects, whereas the urinary FDP D-dimer levels in patients with diabetes mellitus were higher than those of normal subjects. 3) In the CGN and NS groups there was a tendency for an increase in the level of urinary FDP D-dimer in more active forms of the disease. 4) A significant correlation between urinary FDP D-dimer and urinary protein in the CGN and NS groups was demonstrated. 5) In all of the renal diseases investigated in this study, the ratio of urinary FDP D-dimer to total FDP was less than 4%.