It is possible that abnormalities of intraglomerular coagulation and fibrinolysis are involved in the exacerbation of kidney diseases. Urinary fibrin/fibrinogen degradation products (FDP) are regarded as an index of the intraglomerular coagulation and fibrinolysis. Although the conventional latex agglutination method for detecting urinary FDP has disadvantages such as a poor sensitivity and is of the semiassay type, latex photometric immunoassay (LPIA), a recently developed technique, is an assay with a high sensitivity. The present study was undertaken in an attempt to clarify the significance of urinary FDP as measured by latex photometric immunoassay in renal diseases. The subjects comprised were 60 patients with 15 kinds of renal diseases. Occasional urine samples and blood samples withdrawn at the time of urinary collection were examined. The FDP and FDP-E fractions (FDP-E) were measured by LPIA, and the FDP-D fraction (FDP-D) and fibrinopeptide A (FPA) were measured by enzyme immunoassay. The highest level of urinary FDP was seen in cases with diabetic nephropathy, followed by renal amyloidosis and chronic glomerulonephritis. While no correlation was noted between the urinary FDP levels and blood FDP levels, positive correlations were observed among the urinary protein, urinary FDP-E, FDP-D and FPA. The urinary FDP also revealed an inverse correlation with the l/serum creatinine. All cases with high levels of urinary FDP displayed renal dysfunction. These findings suggest that quantitative assay of the urinary FDP using LPIA is important for determining the degree of abnormality of intraglomerular coagulation and fibrinolysis in renal diseases.